research article about hearing loss

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• Published: 05 January 2023

Disruptions to the hearing health sector

• Isabelle Boisvert   ORCID: orcid.org/0000-0001-7050-3197 1 , 2 ,
• Adam G. Dunn   ORCID: orcid.org/0000-0002-1720-8209 3 ,
• Erik Lundmark   ORCID: orcid.org/0000-0002-9417-1454 4 ,
• Jennifer Smith-Merry   ORCID: orcid.org/0000-0002-6705-2652 2 ,
• Wendy Lipworth 5 ,
• Amber Willink 6 ,
• Sarah E. Hughes   ORCID: orcid.org/0000-0001-5656-1198 7 , 8 , 9 , 10 ,
• Michele Nealon 11 &
• Melanie Calvert   ORCID: orcid.org/0000-0002-1856-837X 7 , 8 , 9 , 10 , 12 , 13  

Nature Medicine volume  29 ,  pages 19–21 ( 2023 ) Cite this article

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Technological innovation and changes to regulation are disrupting the hearing health sector, with implications for data privacy, product safety and accessibility, and provide challenges and opportunities for equitable hearing health.

It is estimated that over 1.5 billion people worldwide have hearing loss 1 . Beyond its direct effect on communication, hearing loss often coexists with poorer physical and mental health 2 . Disparities in access to hearing healthcare can be experienced by minority ethnic groups and exacerbated by socioeconomic factors 2 . Advanced digital capabilities and new ear-worn devices, alongside radical changes to regulation that enable over-the-counter (OTC) purchasing of hearing aids in the USA, are expected to increase access to hearing devices. To ensure consumer safety and equity of access to hearing healthcare, it is necessary to understand emerging technologies and consumer needs. It is also important to balance the interests of established and new stakeholders, including developers, providers and consumers of products and services and manage the power relationships between them.

Access and affordability

Two major developments are currently disrupting the hearing healthcare sector. First, the technological developments of within-ear wearable devices (known as hearables) have created opportunities for direct-to-consumer models of hearing healthcare 3 , 4 . An example is the Apple AirPods Pro ear buds, which incorporate advanced sound technology similar to what could previously be found only in hearing aids. Second, a strategic call for action by the World Health Organization (WHO) has urged governments worldwide to review their hearing healthcare policies and practices 1 . Both developments aim to provide increased access to hearing-related interventions that can alleviate the pervasive effect of hearing loss on communication, social connection, education, employment, quality of life and health 1 .

The recently published OTC Hearing Aid Rule in the USA (announced as effective from 17 October 2022) 5 is an example of a regulatory change that was made possible because of new technological capabilities, and which aims to remove what is perceived as an unnecessary barrier to access hearing devices. This rule supports the OTC sale of safe and effective hearing aids for mild to moderate hearing loss, without requiring the involvement of a hearing health professional 5 .

Market competition can also improve the accessibility and affordability of technologies. Consumer-focused hearing-related product-development initiatives can now be found in companies such as Nuheara, Google, Apple and Meta (Facebook), with at least the latter two having recruited research audiologists within their teams. This suggests that several companies plan to expand their hearing-related products within a direct-to-consumer market.

Hearing health disruptions

The response to the WHO’s call for action to address hearing loss, rapid technological advances in hearing technologies, and the OTC Hearing Aid Rule in the USA are all expected to transform hearing health services internationally. Those manufacturers, organizations and clinicians who currently benefit financially from the provision of traditional hearing aids are likely to see their market share for such products decrease as consumers with the most common severity of hearing loss (mild to moderate) bring their attention to OTC alternatives.

In response, companies may develop new strategies to influence existing and developing markets. For example, although adults with more severe hearing loss are not targeted by OTC products, this population may become the main consumer target group for existing hearing aid developers. Alternatively, existing hearing aid developers may shift their developments toward OTC products, with limited product development targeted at more severe hearing loss. These commercial decisions of hearing aid developers will take place in parallel to commercial decisions made by developers of cochlear implants that are used by individuals who obtain limited benefits from hearing aids. Market changes may therefore lead to both a decrease in options and more aggressive advertising campaigns for consumers with more severe hearing loss. As with any disruptive technology, regulatory bodies may expect tensions, conflicts and increased lobbying approaches as existing markets are disrupted and new ones develop.

In addition to regulating new forms of advertising and competition, regulatory bodies will need to address the growing risks related to consumer data privacy, data usage and data integrity (meaning the accuracy, completeness and consistency of data) that may come with the integration of further digital health technology within hearing devices 6 , 7 , 8 . These innovations include: hearing aid biosensors and integrated software that can measure hearing, heart and brain activity; hearing aid microphones that can connect to smart home systems; and hearing aid systems that can track the direction of the users’ gaze 4 , 9 , 10 , providing unprecedented data gathering and knowledge potential for the technology developers, which now include big tech companies such as Facebook and Google.

These technological advances are expected to attract large consumer markets, supporting improved communication and connectivity for people with and without hearing loss 4 . These advances will also facilitate already tested means of linking everyday activities to general medical care, which may further blur the distinction between health and non-health data.

Conflicts of interest

Traditional hearing devices such as hearing aids and cochlear implants already incorporate complex digital technologies for speech enhancement, noise cancellation, data-logging and wireless connectivity, and can be linked to electronic health records and rehabilitation support apps. To facilitate the provision of such advanced technologies within clinical services, close relationships have formed and various sale and support agreements exist between hearing device developers and hearing health providers 11 , 12 . These close relationships create an environment in which conflicts of interest can influence the quality and affordability of clinical services and products 13 . This may contribute to long-standing issues around trust in hearing care services 14 . Conflicts of interest related to the sales of hearing devices are of particular concern, as studies show a placebo effect when consumers are deceived to believe that they are trying a new hearing aid 15 .

Surveys suggest that hearing health professionals and consumers disagree on what they consider to be unethical practices 16 , and a correspondingly wide variety of professional practices and regulations have developed across countries to manage potential conflicts of interest related to sales of hearing devices 17 . This spectrum includes hearing health services that are fully covered by public insurances 17 , regulations that prevent hearing health professionals who recommend hearing devices from financially benefitting from the sale of these devices 18 , and practices that permit ownership of hearing health services by device manufacturers and allow sales targets to be set within clinics 19 . These varying regulations have differentially affected the power relationships between consumers, device developers, health professionals who recommend hearing devices and those who benefit financially from device sales 18 , 19 . A direct-to-consumer hearing health market raises further questions about the potential effect of conflicts of interest on individuals with hearing loss.

Another aspect of device sales that influences current clinical practices is that, in many jurisdictions, the cost of hearing devices has been bundled with the costs of the professional services offered by hearing health clinicians 20 . This not only increased the expected cost of hearing devices but also concealed the costs and benefits of hearing health services, as well as the sources of income for hearing health professionals 21 . The ongoing development of hearables and the OTC hearing aid market will affect the way the different healthcare systems and clinicians offer hearing health information and services.

The increased opportunities to collect data from ear-worn devices exacerbate concerns about the interests that determine what data are collected, who has access to these data and for what purposes. For example, user data can be monetized because of its usefulness in advertising and further product development. Therefore, product providers may offer more affordable devices to users in exchange for the data that the devices collect. In such transactions it is important to be mindful of the potential conflicts of interest and power imbalances between users and product providers 7 . Furthermore, exclusive control over what is collected and ownership of the resulting data by the product developers may prevent independent clinicians and researchers from effectively appraising the validity of commercial claims or conducting independent clinical research on intervention benefits. Such exclusive control could therefore stymy the development of algorithms used in hearing health informatics and automation systems 8 .

Equitable hearing care

A range of policies and regulations (Box 1) can affect how different stakeholder groups collaborate within the hearing health sector (Box 2) to provide information, services and interventions for consumers with hearing loss. Access to innovations should be promoted alongside the strengthening of existing systems and establishment of new independent systems to assess and protect the integrity of data 8 , 22 , as well as launching initiatives on transparency of research and education that can be used to inform clinical recommendations, and allocate funding for hearing services and products.

Hearing devices are currently regulated primarily in terms of professional practices, product safety and efficacy, and within the context of competition law. Because of the data collection capabilities of new digital hearing products, regulation should also consider data collection, integrity, access and user privacy 8 , 22 . Device developers, providers and healthcare professionals should focus on furthering health and health equity, which will require attention to power imbalances and structural inequities. Longitudinal studies will be needed to assess the effects of the changes in the hearing health sector on consumer experience, professional roles and clinical service availability across countries with different structural regulations.

Consumer education and support to access hearing services and products will be especially important for people who may be more vulnerable to misleading marketing claims 15 , 23 because of limited digital, health or research literacy. More than 65% of adults aged over 60 have hearing loss, with clear increases in prevalence with every decade of age 1 . Hearing loss is associated with higher risks of dementia and cognitive impairment 1 and deaf and hard-of-hearing people are more likely to experience communication challenges that limit their access to information 24 . Vulnerable groups, including poorer populations, are less likely to access new technologies than less vulnerable groups, and this may contribute to decreased health equity 25 . Hearing loss is also associated with common illnesses such as hypertension and diabetes 1 , and with an increased risk of hospitalization and mortality 26 . Adults with hearing loss are therefore overly represented among patients who receive other health and disability services.

Professional education is required across health and disability sectors to support the communication and safety needs of patients with hearing loss 24 . This will particularly benefit patients who do not receive any hearing care and those who may access direct-to-consumer hearing devices without the services of a hearing health professional such as an audiologist or an otologist. Empowering a broad range of professionals to better support the needs of people with hearing loss could improve engagement and satisfaction with healthcare in general 24 . This could also increase opportunities for adults with hearing loss to receive information and advice that is independent from product sales.

Everyone with hearing loss should have access to reliable and complete information and to independent professional advice when selecting safe, evidence-based and cost-effective hearing and communication support 1 . Tectonic shifts in the landscape of the hearing device and hearing service industries may pose a critical threat to achieving this goal, as well as providing fresh opportunities. Further research is needed on conflicts of interest, gaps in regulation, and the rapid expansion of emerging technologies if the benefits of these innovations are to be realized by all.

Box 1 Domains of policy and regulation that influence the hearing health sector

Box 2 Stakeholders who influence hearing health information, services and products

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Communication Sciences, Sydney School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia

Isabelle Boisvert

Centre for Disability Research and Policy, Sydney School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia

Isabelle Boisvert & Jennifer Smith-Merry

Biomedical Informatics and Digital Health, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia

Adam G. Dunn

Macquarie Business School, Macquarie University, Sydney, New South Wales, Australia

Erik Lundmark

Department of Philosophy, Macquarie University, Sydney, New South Wales, Australia

Wendy Lipworth

Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA

Amber Willink

Centre for Patient Reported Outcome Research, Institute of Applied Health Research, University of Birmingham, Birmingham, UK

Sarah E. Hughes & Melanie Calvert

Birmingham Health Partners Centre for Regulatory Science and Innovation, University of Birmingham, Birmingham, UK

National Institute for Health Research (NIHR), Applied Research Collaboration (ARC) West Midlands, Birmingham, UK

UK SPINE, University of Birmingham, Birmingham, UK

Collaborator with lived experience of hearing loss. Disability Leadership Institute, Sydney, New South Wales, Australia

Michele Nealon

DEMAND Hub, University of Birmingham, Birmingham, UK

Melanie Calvert

NIHR Birmingham Biomedical Research Centre, University Hospital Birmingham and University of Birmingham, Birmingham, UK

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I.B., A.D., E.L., J.S.M. and W.L. conceived and developed the main ideas for this article. I.B. led the writing with substantial contributions from A.D., E.L. and M.C. All authors provided critical input, and approved the final version. M.N. provided a critical review from the perspective of a person with lived experience of hearing loss.

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Correspondence to Isabelle Boisvert .

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Competing interests.

I.B. is a collaborator on projects that receive funding from Cochlear, but maintains academic independence for all research initiatives. S.E.H. receives funding from the NIHR Blood and Transplant Research Unit (BTRU) in Precision Therapeutics, UKRI, National Technical Institute for the Deaf (NTID) COVID-19 Relief Fund, UK SPINE and declares personal fees from Cochlear, Astra Zeneca, CIS Oncolog, and Aparito outside the submitted work. M.C. receives funding from the National Institute for Health and Care Research (NIHR), UK Research and Innovation (UKRI), NIHR Birmingham Biomedical Research Centre, the NIHR Surgical Reconstruction and Microbiology Research Centre, NIHR Applied Research Collaboration (ARC) West Midlands, the NIHR Blood and Transplant Research Unit (BTRU) in Precision Therapeutics, UK SPINE, European Regional Development Fund – Demand Hub and Health Data Research UK at the University of Birmingham and University Hospitals Birmingham NHS Foundation Trust, Innovate UK (part of UKRI), Macmillan Cancer Support, UCB Pharma, Janssen, GSK and Gilead. M.C. has received personal fees from Astellas, Aparito, CIS Oncology, Takeda, Merck, Daiichi Sankyo, Glaukos, GSK and the Patient-Centered Outcomes Research Institute (PCORI) outside the submitted work; and a family member owns shares in GSK. The other authors declare having no relevant competing interests. The views expressed in this article are those of the authors and not necessarily those of their employing institutions.

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Boisvert, I., Dunn, A.G., Lundmark, E. et al. Disruptions to the hearing health sector. Nat Med 29 , 19–21 (2023). https://doi.org/10.1038/s41591-022-02086-6

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• Published: 23 May 2017

Current insights in noise-induced hearing loss: a literature review of the underlying mechanism, pathophysiology, asymmetry, and management options

• Trung N. Le 1 ,
• Louise V. Straatman 1 ,
• Jane Lea 1 &
• Brian Westerberg 1  

Journal of Otolaryngology - Head & Neck Surgery volume  46 , Article number:  41 ( 2017 ) Cite this article

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Noise-induced hearing loss is one of the most common forms of sensorineural hearing loss, is a major health problem, is largely preventable and is probably more widespread than revealed by conventional pure tone threshold testing. Noise-induced damage to the cochlea is traditionally considered to be associated with symmetrical mild to moderate hearing loss with associated tinnitus; however, there is a significant number of patients with asymmetrical thresholds and, depending on the exposure, severe to profound hearing loss as well.

Recent epidemiology and animal studies have provided further insight into the pathophysiology, clinical findings, social and economic impacts of noise-induced hearing loss. Furthermore, it is recently shown that acoustic trauma is associated with vestibular dysfunction, with associated dizziness that is not always measurable with current techniques. Deliberation of the prevalence, treatment and prevention of noise-induced hearing loss is important and timely. Currently, prevention and protection are the first lines of defence, although promising protective effects are emerging from multiple different pharmaceutical agents, such as steroids, antioxidants and neurotrophins.

This review provides a comprehensive update on the pathophysiology, investigations, prevalence of asymmetry, associated symptoms, and current strategies on the prevention and treatment of noise-induced hearing loss.

Exposure to excessive noise is the most common preventable cause of hearing loss. It has been suggested that 12% or more of the global population is at risk for hearing loss from noise, which equates to well over 600 million people [ 1 ]. The World Health Organization estimated that one-third of all cases of hearing loss can be attributed to noise exposure [ 2 ]. Noise-induced hearing loss (NIHL) has long been recognized as an occupational disease, amongst copper workers from hammering on metal, blacksmiths in the 18 th century, and shipbuilders or “boilermakers” after the Industrial Revolution [ 1 , 2 , 3 ].

Without doubt, chronic noise exposure and the resultant cochlear trauma cause hearing loss and tinnitus. In the United States among workers not exposed to noise, 7% have hearing loss, 5% have tinnitus, and 2% are afflicted with both hearing loss and tinnitus. However, among noise-exposed workers the prevalence is significantly higher at 23, 15 and 9%, respectively [ 4 ]. Within a group of one million noise-exposed workers, the highest risk occupations for hearing loss were identified to be those in mining, wood product manufacturing, construction of buildings, and real estate and rental leasing [ 5 ]. Hearing loss was more prevalent among men than women, likely due to a disproportionate number of males in these occupations, and the risk of hearing loss increased with age.

Despite its prevalence, there is still an ongoing debate about the consequence of the noise-induced damage. For many years, the maximum severity of NIHL was argued to be mild to moderate and symmetrical based on pure tone audiograms [ 6 ]. The impact of hearing loss might be underestimated as recent studies have shown evidence for hidden hearing loss and synaptopathy-induced poor speech recognition [ 7 , 8 ]. Furthermore, the additional impact of noise-induced tinnitus and vestibular dysfunction is still not fully elucidated.

The objective of this review is to provide a comprehensive overview of NIHL including the fundamental and advanced pathophysiology, specific investigations, including detailed discussion on asymmetric NIHL, associated symptomatology, available interventions for prevention and treatment.

Pathophysiology of NIHL

Fundamental equal-energy principle.

NIHL is a complex disease that results from the interaction of genetic and environmental factors, but is generally still dictated by the extent of biological damage caused by noise exposure. The total amount of noise to which an individual is exposed can be expressed in terms of energy level. The energy level is a function of the sound pressure of noise (in decibels) and of the duration of exposure over time. The equal-energy principle effectively states equal energy will cause equal damage (in any given individual), such that similar cochlear damage may result after exposure to a higher level of noise over a short period of time as would occur after exposure to a lower level of noise over a longer period of time [ 9 ].

Environmental factors

For environmental exposure, hearing loss can be caused by long-term, continuous exposure to noise and is generally referred to as NIHL. However, hearing loss can also result from single or repeated sudden noise exposure, which is generally referred to as acoustic trauma. Exposure to sudden impulse noise is more detrimental than exposure to steady state noise [ 10 ]. This review is largely focussed on the former.

Noise trauma can result in two types of injury to the inner ear, depending on the intensity and duration of the exposure: either transient attenuation of hearing acuity a.k.a. temporary threshold shift (TTS), or a permanent threshold shift (PTS) [ 11 ]. Hearing generally recovers within 24–48 h after a TTS [ 12 ]. However, recent studies using a mouse model have found TTS’s at young ages accelerated age-related hearing loss, even though the hearing thresholds were completely restored shortly after the TTS [ 13 ]. Longitudinal data on the impact of TTS’s on the human ear, however, are lacking.

The recovery of TTS is probably a result of reversible uncoupling of the outer hair cell stereocilia from the tectorial membrane [ 14 ] and/or reversible central gain increase and associated hyperacusis and tinnitus [ 15 ]. However, even when there is recovery of auditory pure tone thresholds, there can be considerable damage to the ribbon synapses, a rapid degeneration termed synaptopathy [ 7 , 8 ]. Synaptopathy results in loss of connections between the inner hair cells and their afferent neurons in the acute phase of noise-induced cochlear trauma [ 7 , 16 ], and is most likely a result of glutamate excitotoxicity causing damage to the post-synaptic terminals [ 8 ]. This is also referred to as Noise-Induced Hidden Hearing Loss, as it is not accompanied by a pure-tone threshold shift [ 8 ]. Although the extent to which synaptopathy contributes to NIHL is unknown, it is argued that these synaptopathic mechanisms, similar to synaptopathic disease in certain types of auditory neuropathy, are involved in NIHL [ 17 ]. This is also supported by research in animals showing intact hair cells but extensive noise-induced spiral ganglion loss [ 7 ].

The characteristic pathological feature of NIHL with PTS is the loss of hair cells, particularly the prominent loss of outer hair cells at the basal turn, while loss of inner hair cells was limited. Degeneration of the auditory nerve followed the loss of outer hair cells in both temporal bone histopathology and in a mouse model [ 18 ]. A crucial characteristic of hair cell loss due to any cause (noise, ototoxic medications, age) is the inability of mammalian sensory cells to regenerate [ 19 ].

With sufficient intensity and duration of noise, not only the hair cells but the entire organ of Corti may be disrupted [ 20 ]. Destruction of the organ of Corti can be the result of two mechanisms: mechanical destruction by short exposure to extreme noise intensities or metabolic decompensation after noise exposure over a longer period of time [ 21 ]. Mechanical destruction is acquired by exposure to noise intensities above 130 dB sound pressure level (SPL) leading to disassociation of the organ of Corti from the basilar membrane, disruption of cell junctions, and mixing of endolymph and perilymph [ 22 ]. The pathology observed as a result of metabolic decompensation includes stereocilia disruption, swollen nuclei, swollen mitochondria, cytoplasmic vesiculation, and vacuolization [ 23 , 24 ]. Current theories of metabolic damage center on the formation of free radicals or reactive oxygen species (ROS) and glutamate excitotoxicity evoked by excessive noise stimulation, followed by activation of signalling pathways leading to cell death [ 25 ]. ROS emerge immediately after noise exposure and persist for 7–10 days thereafter, spreading apically from the basal end of the organ of Corti, thus widening the area of necrosis and apoptosis [ 26 , 27 ]. Glutamate is the excitatory neurotransmitter that acts at the synapses of the inner hair cells with the eighth cranial nerve. High levels of glutamate can over-stimulate postsynaptic cells and cause swelling of cell bodies and dendrites [ 28 ], a process referred to as glutamate excitotoxicity.

Another consequence of noise exposure is an increase of free calcium (Ca 2+ ) in outer hair cells immediately after acoustic overstimulation contributed to by both entry through ion channels and liberation from intracellular stores [ 29 ]. Ca 2+ overload can also trigger apoptotic and necrotic cell death pathways independent of ROS formation [ 30 ].

Aside from direct effects on the auditory system, noise also can cause psychological and physiological stress. The hypothalamus-pituitary-adrenal (HPA) axis can modulate the sensitivity of the auditory system and be activated by acoustic stress [ 31 ]. Mice lacking corticotropin-releasing factor receptor (a critical factor in HPA function) in the cochlea exhibited loss of homeostasis and protection against noise-induced hearing loss, leading to an increased susceptibility to noise trauma [ 32 ].

Genetic factors

The genetic susceptibility to NIHL has been clearly demonstrated in animals. Mouse strains (C57BL/6 J) exhibiting age-related hearing loss were shown to be more susceptible to noise than other strains [ 33 , 34 , 35 ]. Also, several heterozygous and homozygous knockout mice including Cdh 23 [ 36 ], Pmca 2 [ 37 ], Sod 1 [ 38 ], Gpx 1 [ 39 ], Trpv 4 [ 40 ], Vasp [ 41 ], and Hsf 1 [ 42 ] were shown to be more sensitive to noise than their wild-type littermates. These studies on knockout mice indicate that there are some genetic deficits that disrupt specific pathways and structures within the cochlea and predispose the inner ear to NIHL.

The discovery of human genetic factors predisposing individuals to NIHL has been hindered by many difficulties. To date, no heritability studies have been performed, since families where all subjects are exposed to identical noise conditions are almost impossible to collect. Hence, another approach involving screening of Single Nucleotide Polymorphisms (SNPs) of different genes known to play a functional and morphological role in the inner ear has been adopted. SNPs are common point mutations in the genome (occurring every 100 – 300 base pairs), and their genotyping is believed to be a successful tool in analyzing the genetic background of complex diseases, such as NIHL. In such studies, a disease susceptibility allele is expected to occur more often among susceptible groups than resistant ones. The most promising results were obtained for the inner ear potassium (K+) ion recycling and heat shock protein (HSP) genes. K+ recycling genes are indispensable for the process of hearing, as evidenced by the fact that multiple mutations in these genes (GJB2, GJB3, GJB6, KCNE1, KCNQ1 and KCNQ4) lead to both syndromic and non-syndromic forms of hearing loss [ 43 , 44 , 45 , 46 ]. HSPs form a group of conserved proteins assisting in synthesis, folding, assembly and intracellular transport of many other proteins. HSPs are ubiquitously expressed in cells under physiological and pathological conditions, and their expression increases under stressful conditions, including noise exposure. When first induced by exposure to moderate sound levels, they can protect the ear from excessive noise exposure [ 47 , 48 , 49 , 50 ]. Three genes are responsible for HSPs synthesis: HSP70-1, HSP70-2 and HSP70-hom. Variations in HSP70-1, HSP70-2 and HSP70-hom genes were shown to be associated with susceptibility to NIHL and these results were replicated in three independent populations, Chinese, Swedish and Polish [ 51 , 52 ]. Recently, the significance of genetic variation in NIHL development has also been shown for otocadherin 15 and myosin 14 genes [ 53 ].

Audiometric investigations

Pure tone audiogram.

Early or moderately advanced NIHL usually results in the typical ‘boilermakers’ notch at 4 kHz, with spread to the neighbouring frequencies of 3 kHz and 6 kHz [ 54 ] and some hearing recovery at 8 kHz [ 6 , 55 ]. The fact that frequencies around 4 kHz are most affected by noise is most likely due to the resonance frequency of the outer ear/ear canal as well as mechanical properties of the middle ear [ 56 ]. High frequencies are also typically affected by presbycusis; therefore the notch may disappear with aging, making it difficult to differentiate NIHL from presbycusis. Whether or not chronic noise exposure can also result in hearing loss at 8 kHz is debated [ 57 ]. With further noise exposure, the notch can get deeper and wider eventually involving lower frequencies such as 2 kHz, 1 kHz and 0.5 kHz [ 58 , 59 ].

Hearing loss induced by noise exposure is quoted to be on average no greater than 75 dB in the high frequencies and no greater than 40 dB in the lower frequencies [ 6 ]. However, chronic noise exposure can in some individuals cause severe to profound sensorineural hearing loss (SNHL). When individual data is reviewed, severe to profound SNHL after noise exposure is documented in noise-exposed individuals with a prevalence varying from 1 to 15% [ 60 , 61 , 62 , 63 , 64 ], well above the prevalence among the general population in the United States (0.5%) and United Kingdom (0.7%) [ 65 , 66 ]. The wide range in prevalence of severe to profound hearing loss found in studies of noise exposed populations may be influenced by underlying genetic factors, or differences in the intensity, type and duration of noise exposure. For instance, SNHL can progress to severe or profound with prolonged durations of noise exposure [ 67 , 68 ], especially in impact noise [ 69 ].

Speech recognition

Traditionally, pure tone thresholds were solely relied upon to determine the extent of NIHL, resulting in an underestimation of NIHL prevalence and functional impact. NIHL can be associated with a decrease in speech recognition scores in quiet as well as in background noise, even in the setting of a normal pure tone audiogram [ 16 ]. This is probably related to the synaptopathic mechanisms, as discussed previously [ 7 , 8 , 16 ] and reduced temporal processing skills [ 70 ] as a result of noise-induced affected connections between inner hair cells and low spontaneous rate auditory nerve fibres, which are important for temporal processing [ 8 ]. In order to quantify noise-induced damage, it is recommended that speech recognition tests in quiet and in noise should be performed in addition to pure tone thresholds [ 7 ].

Otoacoustic emissions (OAEs)

Otoacoustic emissions have the necessary features to serve as an objective, sensitive, and easy-to-administer tool for the diagnosis of NIHL. In laboratory animals exposed to high noise levels, OAE amplitude reductions showed a good correlation with permanent threshold shift of more than 25 to 35 dB SPL measured by auditory evoked potentials and significant outer hair cell loss measured by histologic cochleograms [ 71 ]. Parallel decreases in pure-tone sensitivity and OAE amplitudes were reported among noise-exposed industrial workers and military personnel [ 72 , 73 , 74 ]. In a large sample of subjects with NIHL and normal hearing ears, the presence of click-evoked OAEs at 2 and 3 kHz could distinguish the two groups with 92.1% sensitivity (correct discrimination of NIHL) and 79% specificity (correct discrimination of normal audiogram) [ 75 ]. Similarly, distortion-product OAEs at 2, 3 and 4 kHz yielded 82% sensitivity and 92.5% specificity. Several studies have suggested that OAEs may provide an early indication of noise-induced cochlear damage before evidence for NIHL appears in standard audiometry [ 76 , 77 ]. However, OAEs can only be used to monitor hearing effectively when there is room for hearing deterioration; hence, audiometry is indispensable in the presence of a pre-existing hearing loss and/or when OAEs are low or absent [ 78 ]. OAEs might be more sensitive (and perhaps very useful) with regard to detecting NIHL at an earlier, “pre-clinical” stage, although more data is needed to establish well-defined criteria for the successful use of OAEs in this clinical setting.

Objective measures for noise-induced-synaptopathy

Electrophysiologic measurements such as ABR have been used to detect noise-induced synaptopathy [ 79 ]. There is evidence that suprathreshold wave 1 ABR responses reduced after noise exposure in animals with normal auditory thresholds, at the frequencies tonotopically related to the synaptic loss [ 80 , 81 ]. Therefore it is suggested that wave 1 of the ABR can be predictive to the degree of synaptopathy [ 80 , 81 ]. However, studies in human subjects have yielded conflicting results with some studies providing evidence for wave I reduction as a function of noise exposure [ 82 ], whereas others do not [ 83 ]. This variation in outcome might be caused by lack of sensitivity of ABR testing perhaps due to variations in ABR electrode placement [ 84 ], which makes the usage of wave I as a diagnostic test for cochlear synaptopathy in humans less ideal [ 85 ].

Emerging evidence suggests that acoustic reflex testing may be helpful for early detection of noise-induced synaptopathy in humans. Threshold shifts in acoustic reflexes, without audiometric hearing loss, might be caused by synaptopathy [ 86 , 87 ]. Whether or not acoustic reflexes can be used to assess synaptopathy in humans requires further research.

Asymmetric NIHL

The typical pattern of hearing loss resulting from acoustic trauma is symmetrical [ 6 ]. However, there is increasing evidence that asymmetrical hearing loss occurs as well (Table  1 ). Asymmetry in NIHL generates some controversy in both clinical as well as medico-legal contexts and hence warrants an in-depth discussion.

Evidence for asymmetric NIHL

A recent systematic review concluded that the evidence for asymmetrical noise-induced trauma was limited, however only studies that reported an asymmetry of more than 15 dB were included [ 88 ]. In the general population, the incidence of interaural threshold difference of 15 dB or more is only 1% [ 89 ], whereas the incidence of asymmetrical hearing loss in noise-exposed individuals varies widely between 4.7 and 36% (Table  1 ). Asymmetries between left and right hearing thresholds are typically small (less than 5 dB) [ 90 , 91 ] with a trend toward increasing asymmetry among higher frequencies or with increasing levels of hearing loss [ 92 ]. There is a margin of error for audiometric testing of ± 9.6-14.2 dB for single frequencies, with the largest range reported at 4 kH [ 93 ], which needs to be considered when documenting asymmetric hearing loss. Furthermore, these small differences are based on mean hearing thresholds of group data, which probably underestimates the asymmetric effect of noise exposure at the individual level.

It is worth considering some study findings in more detail. In a study of 208 patients, Fernandes et al. identified asymmetrical hearing loss in 22.6%, of which 6.4% had a definite history of asymmetrical noise exposure and in whom 60% had greater hearing loss in the left ear [ 94 ]. Chung et al. found a prevalence of asymmetrical hearing loss in 4.7% among 1461 patients with noise-induced hearing loss and the left ear was affected more in 82.6% [ 95 ]. Alberti et al. found a 15% prevalence of asymmetrical hearing loss in 1873 patients referred for compensation assessment, and concluded that 36% of patients with asymmetrical hearing loss were attributable to noise exposure, due to a definitive pattern of hearing loss and a history of noise exposure [ 1 ]. In truck drivers, asymmetrical hearing loss has been attributed to noise and air rushing from the opened window [ 96 ]. Chung et al. showed that intensity of noise exposure from sawing wooden blocks into shingles was comparable between both ears, but their data also showed a small but significant asymmetric hearing loss, worse on the left side, that correlated with age and lifetime noise exposure when compared to the industrial population [ 97 ]. In addition, a significant asymmetrical hearing loss of up to a >20 dB difference was found in different studies of populations evaluating symmetrical noise exposure [ 98 , 99 , 100 ]. Major limitations of these studies include reliance on self-reported historical exposures to noise, limited data on the extent of noise exposure, inconsistent criteria for the diagnosis of asymmetrical hearing loss, small sample size, lack of a control group without noise exposure, and lack of direct measures of the physiology of the ear over time.

Studies over the last two decades using industrial or continuous noise exposures have found that noise affects the left ear more than the right ear [ 101 , 102 ]. A similar observation was reported for exposure to impulse sounds, such as gunshots [ 63 , 103 ]. Interestingly, other studies have found no significant correlation between usage of firearms and asymmetry of hearing loss, although the left ear was exposed to more of the noise of the gun blast [ 101 , 104 ]. Tinnitus was also reported to be more frequent in the left ear than the right ear [ 105 , 106 ]. The lateral difference with hearing in the left ear being worse than the right increases with frequency and reaches a peak at 3–6 kHz. In fact, correlation studies looking at 2 kHz asymmetry suggest that as more frequencies are considered, more patients with asymmetrical hearing loss are likely to be found, and the degree of asymmetry can be more precisely delineated [ 95 ]. Chung et al. reported the left ear to be most susceptible to noise at 2 kHz, which may account for a small but significant interaural threshold difference [ 95 , 97 ]. Pirila et al. reported damage to the left ear to be more prominent in men than in women [ 107 , 108 ], whereas Nageris et al. found no such difference. With regard to age, Pirila et al. noted that in children aged 5 to 10 years, there was no left or right predominance in hearing loss [ 109 ]. They postulated that the difference developed later in life and was at the level of the inner ear. Other groups also noted no effect of left- or right-handedness on hearing loss asymmetry [ 63 , 103 ].

Pathophysiology of asymmetric NIHL

Asymmetry in NIHL could theoretically be caused by ambient exogenous noise-exposure factors or by endogenous or anatomical factors. For instance, differentially shielding the right ear from noise or acoustic-energy emitting sources, termed the head shadow effect, may play a role in asymmetric hearing loss [ 110 ]. Significant asymmetry will theoretically occur if the noise source is closer in proximity to one side than the other, for instance in workers using hand-held tools predominantly in one hand [ 111 ] or in military personnel with weapon noise exposure [ 103 ]. The handedness of the subject should thus be of relevance. Since most individuals are right-handed, the muzzle blast from a shotgun reaches the left ear at a higher level than the somewhat shielded right ear. However, studies assessing the impact of handedness on hearing loss showed no correlation between the ear with the asymmetry and the individual’s handedness [ 63 , 103 ]. Several confounding factors are of relevance though. Some left-handed subjects have always fired right-handed or have changed from left to right during their careers; some rifles in use are now right-hand fire only. For most other weapons, the firing position is fixed and therefore the amount of noise exposure to each ear is determined by the head position relative to the weapon [ 92 ]. Other factors to be taken into account include the unilateral use of ear defenders, such as in radio operators where the possible noise hazard or the protective effect can come from use of the headset [ 112 , 113 , 114 ]. In industry, most workers also tend to look over their right shoulder when they operate heavy equipment, and thus their left ear is more exposed to the noise generated by the machine’s engine [ 115 ]. However, the persistent inferiority of the left ear in most of the studied noise-exposed and normal hearing populations suggests that the head shadow effect cannot be the only factor leading to asymmetric NIHL.

Alternatively, the left ear may somehow be more susceptible to NIHL than the right ear, regardless of exogenous noise exposure factors, and this translates into an asymmetric pattern of hearing loss in both noise-exposure and general non-noise exposure populations [ 89 , 103 , 110 ]. The notion that the left ear is the “weaker” ear in most instances is also supported by the fact that tinnitus in the left ear tends to be more magnified than the right ear [ 105 , 106 ]. Individual differences in ear anatomy and physiology, or differences in biological recovery from noise exposure may be responsible. Johnson and Sherman examined the acoustic reflex mechanism given its role as a major protective vehicle against acoustic trauma [ 116 ]. In children aged 6 to 12 years with normal hearing, it was discovered that the acoustic reflex threshold in the right ear was 3 to 7 dB lower than the left ear [ 116 ]. However, this finding was not able to be replicated in adults [ 95 ]. Arguably, the protective effect of the stapedial reflex is most efficient in the low frequency range, and may not be as important at frequencies higher than 2 kHz [ 117 , 118 ]. In short, the protective role of the efferent pathways to cochlea and the possible left-right asymmetries in this system need further research [ 119 , 120 ].

Clinical relevance of asymmetric NIHL

Unilateral or asymmetrical sensorineural hearing loss is important to discern, as it can be a hallmark symptom/sign of a retrocochlear lesion (i.e. vestibular schwannoma), and in such cases further investigation is required (i.e. MRI scan) unless there is a known reason for the asymmetry [ 121 ]. Hence, recognition of asymmetrical hearing due to noise exposure through careful history taking may optimize more appropriate cost-effective investigation of patients.

Conventional teaching suggests that a claimant for compensation who has occupational hearing loss with asymmetrical hearing thresholds is unlikely to have a noise-induced hearing loss in the worse ear, and like any other patient, should be investigated for the ‘other’ cause of the asymmetry. However, given the multitude of recent evidence in the literature, if the asymmetry under question cannot be explained by causes other than noise, and the MRI scan does not reveal another cause, then the decision given should be in favour of the worker, on the basis of benefit of doubt [ 94 ] as the asymmetry may represent a lateral difference in susceptibility to noise damage.

Beyond hearing loss: associated symptomatology

Nihl and tinnitus.

The prevalence of tinnitus among noise-exposed workers is much higher (24%) than the overall population (14%) [ 122 ], and is exponentially higher in those in the military, up to 80% [ 123 ]. Although the majority of individuals with NIHL present with bilateral tinnitus, unilateral tinnitus is reported as well, with a prevalence of up to 47% [ 124 , 125 , 126 ]. Tinnitus is more prevalent on the left side [ 124 , 125 ] consistent with the asymmetry documented in NIHL. The severity of the tinnitus may be associated with the degree of NIHL [ 126 , 127 ]. The impact of tinnitus has been demonstrated: apart from tinnitus being associated with other comorbidities, such as anxiety, depression and sleep disorders [ 128 ], noise-induced tinnitus negatively effects the quality of life in workers [ 129 ] and for military personnel, tinnitus can be distracting during a military operation [ 123 ].

NIHL and vestibular dysfunction

There is increasing evidence for noise-induced vestibular deficiency, through a mechanism of noise-induced damage to the sacculocolic reflex pathway and/or damage to the vestibular hair cell cilia [ 62 , 130 ]. This is supported by multiple studies in human and animals.

In humans, several studies, with relatively small sample sizes ( n  = 20-30), showed that abnormal (reduced, delayed or absent responses) cervical vestibular evoked myogenic potentials (VEMPs) and ocular VEMPs are associated with chronic or acute acoustic trauma [ 62 , 131 , 132 , 133 ]. This supports the hypothesis that noise causes functional damage to the otolithic organs either directly or indirectly. Also, an association was found between cervical VEMPs and hearing outcome after acute acoustic trauma, therefore it was concluded that abnormal VEMPs might indicate more severe trauma and as a result poorer hearing recovery [ 62 ].

Apart from the otolithic organs, noise induced trauma has been shown to cause substantial stereocilia bundle loss and reduction in baseline firing rates of (horizontal and superior) semicircular canals in animal studies [ 130 , 134 ]. A study of 258 military males identified a strong correlation between vestibular symptoms and abnormal findings on electronystagmography (ENG) testing; the presence of spontaneous, gaze-evoked or positional nystagmus and reduced caloric responses in the worst hearing ear was demonstrated, with significantly more abnormal results of all ENG tests in the asymmetrical NIHL group compared to the group with symmetrical NIHL [ 135 ]. In these patients, reduced caloric responses were measured in the worst hearing ear, with the left ear being more often affected, suggesting that acoustic trauma can cause asymmetric noise-induced vestibular loss. Whether or not individuals with symmetrical hearing loss also have bilateral symmetrical vestibular hypofunction cannot be gleaned from the data as absolute values were not reported. Data from this study not only supports the hypothesis that acoustic trauma can cause damage to the (horizontal) semicircular canals, but also shows evidence for asymmetrical trauma after noise exposure, in line with previously discussed evidence for asymmetric induced hearing loss (see paragraph “ Asymmetric NIHL ”).

In animals, noise exposure resulted in a reduction in stereocilia bundle density in vestibular end organs as well as a reduction in regular vestibular afferent baseline firing rates of the otolithic organs and the anterior semicircular canal [ 130 ]. As a normal vestbulo-ocular reflex was measured, it was concluded that noise-induced vestibular damage can be present even in the setting of normal vestibular tests; comparable to “hidden hearing loss”, this might indicate that noise exposure can also cause “hidden vestibular loss” that cannot be identified due to limitations in current techniques for vestibular assessment. This might explain why normal or marginally abnormal vestibular function tests can be seen in noise-exposed individuals [ 136 , 137 ]. Although the impact of noise-induced vestibular loss is unknown, it may explain why individuals with NIHL may present with balance disorders and dizziness [ 135 , 138 ] and therefore needs to be considered when evaluating the impact of noise-induced trauma.

The socio-economic impact of NIHL

The United States Government Accountability Office report on noise (2011) indicated that hearing loss was the most prevalent occupational health disability in the Department of Defense (DoD) [ 123 ]. The DoD civilian worker compensation costs were approximately $56 million in fiscal year 2003, and Veterans Affairs compensation costs were approximately $1.102 billion in fiscal year 2005 with hearing loss as second most common type of disability [ 12 ]. The World Health Organization reported that hearing loss is in the top three common health conditions related to disability in the world as of 2017 [ 139 , 140 ].

The consequences of occupational NIHL to the individual, although not life-threatening, can be dire. Hearing loss limits an individual’s ability to communicate with the surrounding world, which can lead to increased social stress, depression, embarrassment, poor self-esteem, and relationship difficulties [ 59 ]. Social handicap resulting from communication difficulties is exacerbated in difficult listening situations, such as environments with excessive background noise. In addition, longitudinal studies have demonstrated an association between hearing loss and declines in cognition, memory, and attention signifying the importance of prevention and treatment of hearing loss [ 141 , 142 ].

Occupational NIHL has been associated with an increased risk for work-related injuries. For each dB of hearing loss, a statistically significant risk increase was observed for work-related injuries leading to admission to hospital [ 143 ]. Individuals with asymmetrical NIHL may experience decreased ability to localize sounds, which is critical in certain groups of workers like firefighters and other public safety workers, and can be a career-ending disability that has public safety implications as well [ 144 ].

Non-pharmaceutical interventions

Education, regulations, legislation and workplace noise policy.

Prevention remains the best option for limiting the effects of acoustic trauma. Hearing conservation programs in elementary school children are potentially effective to increase the knowledge about the hazards of noise exposure early in life and this may result in behavioral changes towards noise reduction and ear protection [ 145 ]. For industrial noise, elimination or reduction of noise through engineering or administrative controls is the best line of defense. Legislation on occupational noise exposure help to regulate noise exposure and result in noise reduction and/or noise reducing technical improvements to protect employees [ 146 ].

The risk of NIHL can be minimized if noise is reduced to below 80 dB(A) (weighted decibel relative to human ear) [ 147 ]. For higher levels of noise, regulations are necessary as the extent of biological damage correlates directly to the total sound energy level, a function of sound pressure (decibels) and the duration of exposure (time) [ 9 ]. Hearing loss prevention programs establish permissible exposure limits with an exchange rate. The exchange rate defines the number of decibels by which the sound pressure level may be decreased or increased for a doubling or halving of the duration of exposure. This principle is reflected in occupational exposure limits for workplace noise with maximum daily exposure limits halved for every 3–5 dB increase in noise intensity. For instance, assuming an exchange rate of 3 dB, 4 h of exposure at 88 dB(A) is as equally hazardous as 8 h at 85 dB(A).

A recent Cochrane review concluded that in order to prevent occupational hearing loss, better implementation of legislation and better prevention programs are necessary [ 148 ]. Regulations vary widely among different countries and one third of countries in the world still do not have regulations or legislation regarding permissible noise levels and exchange rates [ 149 ]. Most North and South American countries have the permissible exposure limit (PEL) of 85 dB(A) for an 8 h work day [ 149 ]. In some countries (and some provinces in Canada), the PEL is up to 90 dB(A). As TTSs are higher when workers are exposed to 90 dB(A) as compared to 85 dB(A), a standardized reduction of the PEL to 85 dB(A) should be established in order to reduce the prevalence of NIHL [ 150 ]. There is also no international consensus regarding the exchange rate, which varies between countries from 3 dB to 5 dB [ 149 ]. There is evidence, however, that 3 dB overestimates the risk of NIHL and that 5 dB is a better fit [ 151 ]. For impulse noise, there is most often a limit of peak sound pressure level of 140 dB [ 152 ].

Hearing protection

Hearing protection offers a secondary level of protection. However, evidence for effective hearing loss prevention programs (using personal hearing protection) is limited. The most effective hearing protection, including earmuffs and earplugs, can reduce loud noise trauma, but compliance may be limited due to the impact on one’s ability to communicate when they are worn and/or discomfort related to their use [ 153 , 154 ]. To promote the use of hearing protection, different interventional strategies may be beneficial, such as providing general information to motivate workers to use hearing protection or more personalized programmes that provide specific information regarding the risks to the individual worker [ 155 ]. There is a trend towards improved hearing protective device use when a tailored strategy is used that is either situation specific or individual specific, compared to a non-tailored strategy [ 156 ]. Hearing protection with lower attenuation but higher comfort is more efficient than protection with higher attenuation but lower comfort due to compliance issues [ 157 , 158 ]. Custom earplugs have a more consistent attenuation than non-custom earplugs, and user training can improve consistency [ 159 ]. Individual fit-testing, which measures the effectiveness of hearing protection devices specifically for each individual, can be invaluable, particularly with earplugs since they are generally less consistent in noise reduction than ear muffs [ 160 ]. For earmuffs, new materials and design can potentially improve comfort and hearing protection. A recent published study using 3D printed earmuffs showed that the use of light materials like acrylonitrile butadiene styrene/clay nanocomposites can reduce the weight of earmuffs without reducing the attenuation performance [ 161 ]; such technological advancements have the potential to increase comfort and improve compliance.

Pharmacological treatments

Anti-inflammatory effects of corticosteroids to reduce noise induced trauma.

Different types of pharmaceutical agents have been shown to reduce the risk of hearing loss secondary to acoustic trauma. Steroids, specifically intratympanic dexamethasone, may have a therapeutic beneficial effect on NIHL when given before [ 162 ] or after [ 163 ] acoustic trauma in animals. Although an effect is shown in a wide range of dosages, higher dosages appear to be associated with better hearing preservation [ 162 ].

Different routes of delivery have been investigated in animals, including intratympanic, intraperitoneal and direct administration into the scala tympani, and all have demonstrated protective effects as evidenced by preserved hearing (15–20 dB lower hearing thresholds on auditory brainstem response (ABR) measurement and preserved cochlear architecture [ 163 , 164 ]. Each route of delivery may protect hearing at a different level; intratympanic administration appears to be more protective for the efferent terminal outer hair cells synapses, whereas intraperitoneal injections are more protective for the organ of Corti and stria vascularis architecture [ 163 ]. Accordingly, there appears to be a synergistic benefit from the administration by both routes when treating NIHL [ 165 ]. In human studies, it has been shown that after acoustic trauma, the administration of systemic with intratympanic steroid treatment results in better hearing outcomes than with systemic steroids alone [ 165 , 166 ]. Although there is some evidence for a protective effect of steroids in acute acoustic trauma, clearly it is not a long-term option for chronic occupational noise exposure considering the negative side effects of systemic long-term steroid usage.

Antioxidants to reduce oxidative stress

Antioxidants may be a safer alternative to steroids given a more favourable side effect profile. Free oxygen radicals and oxidative stress are important in the pathogenesis of the NIHL, and therefore antioxidants could theoretically constitute an effective treatment.

N-acetylcysteine (NAC) has been reported to reduce the ototoxic effects of noise exposure in animal models [ 167 , 168 , 169 , 170 , 171 ]. In humans, however, the data is limited [ 172 , 173 , 174 ]. Doosti et al. evaluated TTS in 48 textile workers and showed that daily oral administration of NAC (1200 mg/day) during continuous noise exposure prevented the occurrence of a TTS after 14 days of treatment, whereas the untreated group showed a TTS of approximately 1.5–3 dB [ 172 ]. Lin et al. also found a significant improvement in TTS after NAC (1200 mg/day for 14 days). However, the mean difference in TTS in the placebo-treated group versus NAC-treated group was only 0.3 dB [ 175 ]. Kramer et al. did not find a significant protective effect of NAC when using a single lower dose (900 mg PO) administered before noise exposure [ 173 ]. A more recent randomized, double-blinded, placebo-controlled trial among a larger military group (n = 566), found a 6–7% reduction in hearing threshold shift rate, with a total daily dose of 2700 mg of NAC after noise exposure for 16 days during weapon training, but this was only statistically significant when handedness was taken into account (i.e. evaluating the effect on the right ear only in right handed participants). In summary, there is potentially a small benefit of NAC in reducing the rate of threshold shift in a noise-exposed population [ 176 ].

Other antioxidants that can potentially play a protective role against noise-induced cochlear trauma include ginseng [ 172 ], co-enzyme Q10 [ 177 ], as well as several vitamins, such as vitamin A [ 178 ], vitamin C [ 179 , 180 ], vitamin E [ 181 , 182 ], and vitamin B12 [ 183 ]. Studies in animals showed a protective benefit from combination antioxidant treatment, such as magnesium and vitamin A, C, and E [ 184 ], possibly due to synergistic effects [ 185 , 186 , 187 ], These studies were mainly performed in animals or in small groups of humans and the results should be considered preliminary. The efficacy of combining treatments in humans is still unknown.

Neurotrophins for recovery of ribbon synapses

There is evidence in animals that neurotrophins can offer protective effects against noise trauma [ 188 , 189 , 190 , 191 ]. Neurotrophin-3 (NT3) and brain derived neurotrophic factor (BDNF) are important for formation and maintenance of hair cell ribbon synapses in the cochlea, as well as in the vestibular epithelia [ 190 ]. NT3, derived from supporting cells, promotes the recovery of the number of ribbon synapses as well as their function after noise-induced trauma [ 189 , 190 ]. A dose-dependent effect was found of glial cell-derived neurotrophic factor (GDNF) on sensory cell preservation as well as ABR confirmed hearing threshold, after chronic application of GDNF (10 and 100 ng/ml) through a cochleostomy in the scala tympani via a micro-osmotic pump. However, this effect was small and appears to be associated with some toxicity at a higher concentration (1 μg/ml) [ 188 ]. Even a single application of NT3 and BDNF on the round window, immediately after noise trauma, can potentially reduce the synaptopathy (indicated by increased number of presynaptic ribbons, postsynaptic glutamate receptors, and co-localized ribbons) and recover hearing [ 191 ]. Another approach is transplantation of neurotrophin-secreting olfactory stem cells into the cochlea, which also caused restoration of noise-induced hearing loss [ 192 ]. Although these results are promising, long-term effects are still unknown and no studies in humans have been performed to date.

Other pharmaceutical agents

Other pharmaceutical agents with possible protective NIHL effects include magnesium and statins. A human study [ 193 ] as well as research on animal models [ 194 , 195 ] have shown that acoustic trauma can potentially be minimized by magnesium, as it reduces apoptosis of hair cells by a reduction of calcium flow into the cell, thereby reducing reactive oxygen species formation. A double-blinded, placebo-controlled, crossover trial to assess the effects of prophylactic N-acetylcysteine (600 mg) and magnesium (200 mg) prior to noise exposure is pending [ 196 ].

Statins might prevent NIHL by reducing oxidative stress and improving hair cell survival in animals [ 197 , 198 ]. A significant recovery of TTS (determined by measuring distortion product otoacoustic emissions) was found in rats treated with 5 mg/kg atorvastatin administered daily for 2 weeks prior to 2 h of noise exposure [ 199 ].

Surgical treatment

Cochlear implantation.

Due to the severity of the hearing loss and/or the poor speech recognition due to synaptopathy, some individuals with NIHL might eventually become candidates for cochlear implantation (CI) either with full electrical or with electro-acoustic stimulation (EAS). Studies have reported NIHL as the etiology of deafness in implanted individuals, with a prevalence ranging from 2% (CI) to 20% (CI with EAS) [ 200 , 201 ]. This may underestimate the true prevalence, considering the high percentage of unknown etiologies approximating 40–50% of CI recipients [ 200 ]. Currently we can only speculate on the extent to which the SNHL in these implanted individuals can be attributed to noise exposure or due to a combination of other underlying predisposing factors.

The impact of noise-induced hearing loss is more widespread than has previously been recognized. Apart from a wide range of hearing frequencies that can be adversely affected by noise exposure, there is increasing evidence that noise-induced synaptopathy causes reduced speech perception in noise, even when pure tone thresholds are still preserved (“hidden hearing loss”). Evidence in the current literature further supports the notion that noise exposure can result in an asymmetric pattern of hearing loss due to unique differences in susceptibility to noise damage within individuals, increase frequency of tinnitus as well as vestibular dysfunction. The left ear (hearing and balance) is more adversely affected by noise, even in the presence of symmetric noise exposure. Future studies should focus on underlying mechanisms that lead to the susceptibility of left-right asymmetry, and to understand the protective role of the efferent pathways to the cochlea as demonstrated in gender differences. Primary prevention with a focus on regulations, legislation and education in schools, in combination with proper hearing protection are important first lines of defense. Further human studies are needed to address the effectiveness of pharmaco-therapeutic options to prevent or mitigate noise-induced trauma.

Abbreviations

Auditory brainstem response

A-weighted decibel

Electronystagmography

N-acetylcysteine

• Noise-induced hearing loss

Otoacoustic emissions

Permissible exposure limit

Permanent threshold shift

Reactive oxygen species

• Sensorineural hearing loss

Sound pressure level

Transient threshold shift

Vestibular evoked myogenic potentials

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Le, T.N., Straatman, L.V., Lea, J. et al. Current insights in noise-induced hearing loss: a literature review of the underlying mechanism, pathophysiology, asymmetry, and management options. J of Otolaryngol - Head & Neck Surg 46 , 41 (2017). https://doi.org/10.1186/s40463-017-0219-x

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Association between hearing loss and cognitive decline in the elderly: A systematic review with meta-analysis study

Roles Conceptualization, Data curation, Investigation, Methodology, Project administration, Writing – original draft

Affiliation Health Sciences Center, Federal University of Recôncavo of Bahia, Bahia, Brazil

Roles Conceptualization, Data curation, Methodology, Validation, Writing – original draft, Writing – review & editing

Affiliation Department of Health, Feira de Santana State University, Bahia, Brazil

Roles Methodology, Validation, Visualization, Writing – review & editing

Roles Conceptualization, Funding acquisition, Methodology, Supervision, Validation, Writing – original draft, Writing – review & editing

Roles Conceptualization, Data curation, Supervision, Writing – review & editing

Affiliation Federal Institute of Education of Bahia—Lauro de Freitas, Bahia, Brazil

Roles Formal analysis, Investigation, Methodology, Writing – original draft

Roles Methodology, Supervision, Writing – original draft, Writing – review & editing

Roles Conceptualization, Data curation, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

Roles Conceptualization, Formal analysis, Methodology, Resources, Supervision, Validation

Affiliation Epidemiology Surveillance, Federal District Health State Secretariat, Brasilia, Distrito Federal, Brazil

Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

* E-mail: [email protected]

• Débora Conceição Santos de Oliveira, 
• Isaac Suzart Gomes-Filho, 
• Edna Maria Araújo, 
• Michelle de Santana Xavier Ramos, 
• Julita Maria Freitas Coelho, 
• Adan Araújo Marques, 
• Alexandre Marcelo Hintz, 
• Dóris Firmino Rabelo, 
• Ana Claudia Morais Godoy Figueiredo, 
• Simone Seixas da Cruz

• Published: November 9, 2023
• https://doi.org/10.1371/journal.pone.0288099
• Reader Comments

Hearing loss has been pointed out as a potential predictor for cognitive decline. This study conducted a systematic review to evaluate the scientific evidence on the association between hearing loss in the elderly and cognitive decline, as well as whether race/color influences this relationship.

The search for studies was performed in the following electronic databases: MedLine/PubMed Web of Science, Scopus and Virtual Health Library, and MedRkiv up to August 2022. Studies with epidemiological designs that assess the association between hearing loss and cognitive decline in the elderly were eligible for inclusion. Three independent reviewers performed the selection, data extraction and evaluation of the quality of the studies using the Newcastle-Ottawa Scale. A meta-analysis using a random effects model estimated the global association measurements (Beta coefficient: β) and their 95% confidence intervals (95%CI), and the Higgins and Thompson indicator (I 2 ) was also estimated to assess statistical heterogeneity among the studies.

5,207 records were identified in the database surveys, of which only 18 were eligible studies, totaling 19,551 individuals. Hearing loss was associated with cognitive decline in the elderly, with statistical significance: β = -0.13; 95%CI = -0.23 to -0.04; I 2 = 98.70%). For black individuals, the magnitude of the association increased: β = -0.64; 95%CI = -3.36 to 2.07; I 2 = 95.65%, but it was not statistically significant.

The findings of this systematic review showed the existence of a significant relationship between hearing loss and cognitive decline in the elderly, as well as signaling that among black individuals the magnitude of the association can be increased.

Citation: Conceição Santos de Oliveira D, Gomes-Filho IS, Araújo EM, Xavier Ramos MdS, Freitas Coelho JM, Marques AA, et al. (2023) Association between hearing loss and cognitive decline in the elderly: A systematic review with meta-analysis study. PLoS ONE 18(11): e0288099. https://doi.org/10.1371/journal.pone.0288099

Editor: Thiago P. Fernandes, Federal University of Paraiba, BRAZIL

Received: January 4, 2023; Accepted: June 19, 2023; Published: November 9, 2023

Copyright: © 2023 Conceição Santos de Oliveira et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper.

Funding: The research was funded by the Foundation for Research Support of the State of Bahia - Brazil (Fundação de Amparo à Pesquisa do Estado da Bahia - FAPESB) and by National Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Projections indicate that, by 2050, life expectancy will be 82 years for men and 86 for women in developing countries [ 1 ]. In Brazil, studies by the Brazilian Institute of Geography and Statistics projected that by 2060, a quarter of the population will be over 65 years old [ 2 ]. This fact engenders complex challenges in taking care of the health of the older person, including their hearing capacity, due to the inversion of the age pyramid.

Hearing loss among the elderly reduces quality of life, due to a decrease in daily activities and sociability, and may generate processes of loss of autonomy, social isolation, depression, and dementia resulting from a cognitive decline that seems to accompany it [ 3 – 6 ].

Impaired hearing and cognition are disabling conditions for the elderly. The impairment of cognitive functions is directly related to an individual´s reduced interaction in their social context, hindering daily life due to detrimental changes to the domains of attention, perception, executive functions, capacity for retention and application of knowledge in daily life [ 7 ]. So far, the effect of using hearing aids on cognitive functions is still unclear, since reports on the effects of using hearing aids have produced inconclusive results, but it is known that hearing aid use can affect immediate cognitive function [ 8 ] and there is recent evidence that long-term use may delay cognitive decline [ 9 ].

Cognitive decline has been indicated as a predictor of severe cognitive diseases such as dementia and can affect up to 33% of older adults aged 85 years and over [ 10 , 11 ]. This scenario is further aggravated by racial disparities in health that, often, black older people have faced throughout their lives [ 12 – 15 ]. Furthermore, evidence indicates that cognitive decline is among the most prevalent mental health problems in elderly black individuals [ 15 ].

The relationship between hearing loss and cognitive decline has already been investigated by some researchers [ 16 – 18 ]. However, the two problems have a complex chain of causality, so the underlying mechanisms that lead to the connection between the two are not yet well understood [ 19 , 20 ]. In addition, there is an insufficient number of studies that investigated the association between hearing loss and cognitive decline in minority populations, such as the elderly black population. Racial/ethnic and socioeconomic disparities exist in hearing health care and represent critical areas for research and intervention [ 21 ].

For the best of our knowledge, there is no systematic review with meta-analysis with a sample composed exclusively of the elderly. Previous systematic reviews involved mixed populations in relation to age group [ 17 , 22 – 24 ]. Thereby, the present systematic review with meta-analysis evaluated the scientific evidence on the association between hearing loss and cognitive decline in the elderly, as well as its magnitude among elderly black individuals.

Registration and protocol

The protocol of this systematic review was registered in the International Prospective Registry of Systematic Reviews—PROSPERO DATABASE: CRD42022340230. This review followed the PRISMA—2020 Statement [ 25 ].

Eligibility criteria for studies

Cohort, cross-sectional, and case-control studies involving people aged 60 years or older were included. Initially, there was no linguistic restriction, and the data collection was conducted from March 4 up to August 1, 2022. Studies without a clear description of the diagnostic criteria for hearing loss and/or cognitive decline, such as those with self-reported information, were excluded. Studies involving samples of elderly people diagnosed with dementia were also excluded.

Information sources

The studies were searched using the following electronic databases; Medline/PubMed, Virtual Health Library—VHL, Web of Science and Scopus. The reference lists of the articles selected for systematic review, as well as specific databases containing texts from the gray literature, such as MedRkiv, were also examined.

Search strategies

The descriptors used and their synonyms were identified in the Medical Subject Headings (Medical Terms Titles)—MeSH. The keywords used for the search strategies were elderly, hearing loss, cognitive dysfunction and cognitive decline. The English terms employed were: Aged, Deafness, Hearing Loss, Cognitive Impairment, Cognitive Dysfunction and Cognitive Decline. The following Boolean operators were employed: AND and OR. The initial search strategy was adapted to the other electronic databases (Chart 1 in S1 File ). To assess the quality of search strategies, the Peer Review Electronic Search Strategy—PRESS was used [ 26 ].

Study selection

All phases of this review were carried out independently by 3 reviewers. Disagreements in the evaluated phases were resolved among them [ 25 ]. After excluding duplicates, the studies were selected by reading titles and abstracts (D.C.S.O., S.S.C., and A.A.M), using the Rayyan program [ 27 ]. The reviewers were unaware of the decisions made by their peers during the selection process of the articles. A.G., A.A.M., and S.S.C. read the full text of the selected articles independently, and those which met the eligibility criteria were included in the systematic review.

Data extraction

The researchers (D.C.S.O., S.S.C., and A.A.M.) performed data extraction from the included articles using the following fields: author’s name, year of publication, place and year of study, objective, study design, sample size, criteria for the diagnosis of hearing loss and cognitive decline, association measurement, presence of confounding and modifier variables and the main findings.

Quality of studies

To evaluate the quality of the selected studies, the Newcastle—Ottawa quality assessment scale for cohort, case-control and adapted for cross-sectional studies were used [ 28 , 29 ]. The researchers (D.C.S.O, S.S.C. and A.A.M) performed the quality assessment of all studies, independently, and then the information was confronted until a consensus was reached among them.

Data analysis

Quantitative data analysis used Stata version17® statistical package (StataCorp LLC, College Station, TX, USA). Higgins and Thompson’s I-square indicator (I 2 ) was used to evaluate statistical heterogeneity among studies [ 30 ]. To interpret the magnitude of the inconsistency of the data among the studies included in the meta-analysis, the percentage score of test I 2 was used as follows: 0% to 40%: it may not be important, as it may indicate slight heterogeneity; 30% to 60%: moderate heterogeneity; 50% to 90%: substantial heterogeneity; 75% to 100%: very substantial heterogeneity. The diagnosis of the origin of heterogeneity was also performed in the studies, using visual inspection of the Galbraith chart [ 31 ]. Eventual publication biases were evaluated by inspection performed using the of the Begg funnel chart [ 32 ].

The selection of statistical methods considered the data of the association measurements between hearing loss and cognitive decline–expressed in the Beta coefficient ( β ) and its 95% confident interval (95%CI) of the linear regression model between the continuous variables of exposure and outcome. The estimates of coefficient β were standardized using Cohen’s d function [ 33 ].

At the end of the search, 5,207 records were identified. Duplicate records were removed for reading titles and summaries. Of these, 504 articles were selected for complete reading and 18 articles met the eligibility criteria of this systematic review ( Fig 1 ).

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• TIFF original image

https://doi.org/10.1371/journal.pone.0288099.g001

Qualitative analysis

The 18 studies considered for this review included 19,551 participants. Of which, for the analysis of the association between hearing loss in the elderly and cognitive decline, regardless of race/color, 17 articles totaled 19,407 elderly people, consisting of meta-analytical model I [ 34 – 50 ] ( Fig 2A ).

https://doi.org/10.1371/journal.pone.0288099.g002

When considering the influence of race/color on the association, only 3 studies were included [ 37 , 38 , 40 ], with a total of 1,333 participants, representing meta-analytical model II ( Fig 2B ).

In both models, the investigations were observational. In meta-analytical model I, the number of studies were 6 (35.3%) cross-sectional, 10 (58.8%) cohort and 1 (5.9%) case-control. Most investigations occurred in the North American region 9 (52.9%). The others were developed in Asia.

In addition, in the aforementioned model, 16 (88.2%) presented ≤ 25 dB as a criterion of normal hearing level, 1 (5.9%) ≤ 40 dB and 1 (5.9%) ≤ 20 dB. Regarding the diagnosis of cognitive decline, 10 records (58.2%) used the Mini-Mental State Examination [ 51 ]; and 7 (41.2%) used other tests for definition ( Table 1 ).

https://doi.org/10.1371/journal.pone.0288099.t001

However, for meta-analytical model II, all studies were conducted in North America 3 (100.0%) and were cross-sectional ( Table 1 ). In this model, the criterion adopted for defining hearing loss was greater than 25 dB in the three studies included. Three different cognitive decline definition criteria were used: Mini-Mental State Examination [ 52 ]; a Telephone Interview for Cognitive (TIC) Status [ 37 ] and Consortium to Establish a Registry for Alzheimer’s Disease– CERAD [ 38 ]. Chart 2 in S1 File provides more information about these criteria used to assess cognitive function.

In both models, in general, the evaluation of the quality of the studies was classified as high, with averages of 7.94 (± 0.86). There is variation from moderate to high quality (6 to 9 points), with no article classified as low quality (Charts 3 and 4 in S1 File ). In the selected investigations, covariables age and gender were considered as potential confounding factors in all individual studies.

Hearing loss and cognitive decline

The summary measurement of the meta-analytical model I estimated a significant association between hearing loss and cognitive decline, regardless of race/color (β = -0.13; 95%CI = -0.23 to -0.04), with I 2 of 98.70% representing high heterogeneity among the studies ( Fig 2A ). A Galbraith graph was performed, showing some outlier studies but the removal of these did not change either the association measurement or the value of statistical heterogeneity ( Fig 1 ).

The global association measurement of meta-analytical model II showed that among blacks, although the overall measurement was higher than the previous one, statistical significance was not maintained, and heterogeneity remained high: β = -0.64; 95%CI = -3.36 to 2.07; I 2 = 95.66% ( Fig 2B ).

For the meta-analytical model I, publication bias was investigated and asymmetry in the visual analyses of the included studies were observed ( Fig 2 ).

The main findings of this systematic review with meta-analysis showed that there was an association between hearing loss and cognitive decline in the elderly, regardless of race/color, statistically significant. As far as we know, this is the only systematic review with meta-analysis with a sample composed exclusively of the elderly. The present study presented results similar to those published in previous systematic reviews, which involved mixed populations in relation to age group [ 17 , 22 – 24 ].

The mechanisms that can promote hearing loss, and, subsequently, become a risk factor for cognitive decline in the elderly, have not yet been completely clarified [ 17 ]. Some scholars argue that the degradation of the vascular system in the course of life is an underlying factor, which predisposes the elderly to both hearing loss and cognitive decline, since in the course of life, in general, there is physiological reduction of auditory and brain functions [ 52 ].

However, others argue that the reduction of auditory acuity generates difficulties in speech perception, reducing the speed of processing and understanding of language and, consequently, leading the individual to have memory loss, lack of attention and difficulty in developing logical thoughts. According to the above-mentioned theory, there is an important causal relationship between hearing loss and cognitive capacity restriction [ 53 – 56 ].

Furthermore, according to this investigation, in relation to the specific analytical measurement target for black elderly, the findings indicated that the magnitude of the global association measurement (β = -0.64) between hearing loss and cognitive decline was approximately 5 times higher than that estimated in the model in which the item race/color was not considered (β = -0.13). However, there was no statistical significance of the association among black elderly, probably because there were only 3 individual investigations [ 37 , 38 , 40 ], which presented different characteristics of the population groups involved, with a sample size, which, even having been increased through this meta-analysis, did not have enough power to answer the hypothesis raised.

It is important to highlight that of the synthesis studies that evaluated the association, none of them presented the specific meta-analytical measurement for race/color. The absence of these measurements in previous studies is the main finding of this meta-analysis. Although it is recognized that there are weaknesses in this inference, due to the low statistical power conferred by the insufficient number of studies and the high estimated heterogeneity among them [ 57 ].

However, in synthesis investigations, the absence of scientific evidence of quality, according to specific characteristics such as race/color, may be reflections of scarce and limited individual studies on the topic. In other words, the gap in knowledge cannot categorically mean the absence of the influence of race/color on the association between hearing loss and cognitive decline.

This gap may represent an important obstacle to the diagnosis of the auditory health situation of black elderly, since rational decision-making in health, which aims to combat racial inequities, should be based on qualified scientific evidence [ 58 – 61 ].

Although the information resulting from the research, disaggregated by race/color, has been neglected throughout the history of Health Sciences [ 62 ], this scenario is changing slowly, in Brazil and in the world. It has already been recognized that the research of health problems by race represents an important step towards the creation of an indispensable process of deconstruction of the centuries old social structure which weakens the black population and promotes the maintenance of health inequities [ 59 , 60 , 62 ].

Regarding the high heterogeneity identified in the two meta-analysis models, this can be attributed to the different classification systems of cognitive decline, different types of methodological designs and the peculiarities of the sociodemographic characteristics of the population groups that comprised the samples of the individual studies. Most of the selected studies used the Mini-Mental State Examination to diagnose cognitive decline and approximately 40% used other tests that must have contributed greatly to the difference between them. It is known that substantial measurements of heterogeneity in meta-analysis may represent the existence of bias in global estimates and, for this reason, constitute a source of concern with the evidence found [ 57 ].

On the other hand, it is noteworthy that the methodological quality of the included studies was generally considered moderate to high, which represents one of the strengths of this meta-analysis [ 25 ]. There was an effort on the part of the studies to present adjusted measurements for potential classic confounding, such as age, gender and vascular factors, through the use of multiple analysis, giving greater robustness to the overall results [ 63 ].

As positive elements of this systematic review, we mention the insertion of five bibliographic bases, with studies of moderate to high methodological quality—in addition to the use of tools and procedures already validated in the scientific environment for studies of this nature. In this sense, the Peer Review of Electronic Research Strategies (PRESS [ 26 ] was used as an instrument to evaluate the quality of research strategies, in an attempt to increase the reliability of the selection of studies.

It was not the objective of this study, but it is suggested that future systematic reviews assess the possible factors that may influence cognitive decline, such as the type of hearing loss, mixed and sensorineural, as well as its laterality, that is, bilateral or predominantly unilateral. These factors are believed to have an impact on cognitive impairment. The accurate classification of hearing loss provides valuable insights into underlying mechanisms, potential risk factors, and appropriate interventions. This will contribute to a better understanding of the diverse effects of hearing loss within specific subgroups of the elderly population and aid in the development of personalized strategies for prevention and intervention. In addition, another relevant issue that needs to be investigated is the effect of using hearing aids on cognitive functions, since it is known that hearing aid use can affect immediate cognitive function [ 8 ] and there is recent evidence that long-term use may delay cognitive decline [ 9 , 64 – 66 ].

Finally, it is important to encourage robust scientific investigations that expand the knowledge about the hypothesis of an association between hearing loss and injuries such as cognitive decline in the elderly, without neglecting the valuable information disaggregated by race/ color, particularly in regions with intense racial inequities. The detailed investigation of the true auditory and general health condition of individuals from different groups is a powerful tool in addressing racial disparities.

Supporting information

S1 checklist. prisma 2020 checklist..

https://doi.org/10.1371/journal.pone.0288099.s001

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Hearing Loss and Frailty among Older Adults: The Atherosclerosis Risk in Communities Study

Affiliations.

• 1 Cochlear Center for Hearing and Public Health, Johns Hopkins University, Baltimore, MD, USA; Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. Electronic address: [email protected].
• 2 Cochlear Center for Hearing and Public Health, Johns Hopkins University, Baltimore, MD, USA; Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
• 3 School of Medicine, University of Mississippi Medical Center, Jackson, MS, USA.
• 4 Cochlear Center for Hearing and Public Health, Johns Hopkins University, Baltimore, MD, USA; Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, MD, USA.
• 5 Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
• 6 Department of Otolaryngology-Head and Neck Surgery, University of Washington, Seattle, WA, USA.
• 7 Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC, USA.
• PMID: 37748754
• PMCID: PMC10615781 (available on 2024-11-01 )
• DOI: 10.1016/j.jamda.2023.08.023

Objectives: Hearing loss may contribute to frailty through cognitive and physical decline, but population-based evidence using validated measures remains scarce. We investigated the association of hearing loss with phenotypic frailty and its individual components and explored the potential protective role of hearing aid use.

Design: Cross-sectional study of community-dwelling older adults at visit 6 (2016-2017) of the Atherosclerosis Risk in Communities (ARIC) study, a cohort study of older adults from 4 U.S. communities (Washington County, MD; Forsyth County, NC; Jackson, MS; and Minneapolis, MN).

Setting and participants: Population-based study of 3179 participants (mean age = 79.2 years, 58.9% female).

Methods: Pure-tone audiometry at 0.5-4 kHz was used to assess unaided hearing, and the better-hearing ear's pure-tone average was categorized as follows: no [≤25 dB hearing level (HL)], mild (26-40 dB HL), and moderate or greater (>40 dB HL) hearing loss. Hearing aid use was self-reported. The Fried/physical frailty phenotype was used to categorize frailty status (robust, pre-frail, or frail). Multivariable multinomial and logistic regression models were used to study the association of hearing loss/hearing aid use with frailty status and individual frailty components, respectively.

Results: In our sample, 40% had mild and 27% had moderate or greater hearing loss (12% and 55% reported hearing aid use, respectively). Moderate or greater hearing loss was associated with greater odds of being pre-frail [odds ratio (OR), 1.25; 95% CI, 1.01-1.57] and frail (OR, 1.62; 95% CI, 1.06-2.47) vs robust, and greater odds of having slow gait, low physical activity, and exhaustion, compared with no hearing loss. Among those with hearing loss (>25 dB HL), compared with hearing aid users, nonusers had greater odds of being frail vs robust, and having unintentional weight loss, slow gait, and low physical activity.

Conclusions and implications: Hearing loss is associated with pre-frailty and frailty. Longitudinal studies are warranted to establish if hearing aid use may prevent or delay frailty onset.

Keywords: Fried criteria; Hearing loss; frailty; hearing aids; physical frailty phenotype.

Copyright © 2023 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.

PubMed Disclaimer

Conflict of interest statement

Conflicts of interest:

FRL serves as a volunteer board member of the nonprofit, Access HEARS, is a consultant to Frequency Therapeutics and Apple Inc, and is the director of a public health research center funded partly by a philanthropic donation from Cochlear Ltd. To the Johns Hopkins Bloomberg School of Public Health. NSR is an advisor to Neosensory. For the remaining authors none were declared.

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Masks Strongly Recommended but Not Required in Maryland, Starting Immediately

Due to the downward trend in respiratory viruses in Maryland, masking is no longer required but remains strongly recommended in Johns Hopkins Medicine clinical locations in Maryland. Read more .

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The Hidden Risks of Hearing Loss

Hearing loss is frustrating for those who have it and for their loved ones. But recent research from Johns Hopkins reveals that it also is linked with walking problems, falls and even dementia.

In a study that tracked 639 adults for nearly 12 years, Johns Hopkins expert  Frank Lin, M.D., Ph.D . , and his colleagues found that mild hearing loss doubled dementia risk. Moderate loss tripled risk, and people with a severe hearing impairment were five times more likely to develop dementia.

The Links Between Hearing and Health

“Brain scans show us that hearing loss may contribute to a faster rate of atrophy in the brain,” Lin says. “Hearing loss also contributes to social isolation. You may not want to be with people as much, and when you are you may not engage in conversation as much. These factors may contribute to dementia.”

As you walk, your ears pick up subtle cues that help with balance. Hearing loss mutes these important signals, Lin notes. “It also makes your brain work harder just to process sound. This subconscious multitasking may interfere with some of the mental processing needed to walk safely.” 

Research Shows Many Causes, Early Symptoms

Everything from genes and noise exposure to medications, head injuries and infections can play a role in hearing loss. Trouble detecting soft or high-pitched sounds is often the first sign that stereocilia —the delicate hair cells that convert sound waves into electrical signals within the ear—have been damaged. Soft sounds include phone conversations or background noise in settings such as restaurants. High-pitched sounds may include children’s voices. Ringing in the ears, called tinnitus, is another early signal of possible hearing loss. 

Hearing Aid Myths That Hold You Back

Can hearing aids reduce these risks? Lin hopes to find out in a new study, still in the planning stages. “These studies have never been done before,” he notes. “What we do know is that there’s no downside to using hearing aids. They help most people who try them. And in those people, they can make all the difference in the world—allowing people to reengage with friends and family and to be more involved again.”

Although nearly 27 million Americans age 50 and older have hearing loss, only one in seven uses a hearing aid. If you think your hearing has diminished, it’s worth making an appointment with an audiologist for a hearing check, Lin says. If you have hearing loss, don’t let the following myths keep you from getting help.

“My hearing’s not  that  bad.”

Hearing aid users wait, on average, 10 years before getting help for hearing loss. But during that time, communication with loved ones becomes more difficult, and isolation and health risks increase. “Our findings emphasized just how important it is to be proactive in addressing any hearing declines over time,” says Lin.

“Wearing hearing aids means I’m old, and I’m not ready for that.”

It’s normal to feel worried that hearing loss means you’re aging—and to want to hide it. Plenty of people with a hearing impairment sit silently rather than joining in conversations and activities, because they fear that hearing problems will make them seem helpless or less than competent. The truth: Connecting with others can help your brain stay younger and keep you involved with life.

“I don’t like the way hearing aids look.”

Forget the old days of big, whistling earpieces. Today’s hearing aids and cochlear implants are smaller (and less conspicuous) than ever before. Even celebrities (like former president Bill Clinton and football Hall of Famer Mike Singletary) are wearing them proudly.

“I heard that hearing aids are difficult to use.”

There is a breaking-in period as you—and your central auditory system and brain—adjust to life with hearing aids. That’s why most doctors and hearing centers include a trial period, so you can be sure the type you’ve chosen—whether it’s a miniature behind-the-ear model or one that fits into your ear—is right for you.

Definitions

Social isolation : Loneliness that can affect health. People who are socially isolated have little day-to-day contact with others, have few fulfilling relationships and lack a sense of belonging. Social isolation can increase the risk for poor eating, smoking, alcohol use, lack of exercise, depression, dementia, poor sleep and heart disease.

Dementia (di-men-sha) : A loss of brain function that can be caused by a variety of disorders affecting the brain. Symptoms include forgetfulness, impaired thinking and judgment, personality changes, agitation and loss of emotional control. Alzheimer’s disease, Huntington’s disease and inadequate blood flow to the brain can all cause dementia. Most types of dementia are irreversible.

Cochlear (koe-klee-er) implant : A device implanted into the inner ear to stimulate the auditory (hearing) nerve. It’s used to help restore sound perception in children and adults with profound hearing loss.

What You Need to Know Over-the-Counter Hearing Aids: Frequently Asked Questions

The Food and Drug Administration’s recent rule has expanded access to hearing aids by creating a new category of hearing aids: over-the-counter (OTC) hearing aids. Here are the answers to some of the most commonly asked questions about over-the-counter hearing aids.

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Deafness and hearing loss

• By 2050, nearly 2.5 billion people are projected to have some degree of hearing loss, and at least 700 million will require hearing rehabilitation.
• Over 1 billion young adults are at risk of permanent, avoidable hearing loss due to unsafe listening practices.
• An annual additional investment of less than US$ 1.40 per person is needed to scale up ear and hearing care services globally.
• Over a 10-year period, this promises a return of nearly US$ 16 for every US dollar invested.

Over 5% of the world’s population – or 430 million people – require rehabilitation to address their disabling hearing loss (including 34 million children). It is estimated that by 2050 over 700 million people – or 1 in every 10 people – will have disabling hearing loss.

Disabling hearing loss refers to hearing loss greater than 35 decibels (dB) in the better hearing ear. Nearly 80% of people with disabling hearing loss live in low- and middle-income countries. The prevalence of hearing loss increases with age, among those older than 60 years, over 25% are affected by disabling hearing loss.

Hearing loss and deafness

A person who is not able to hear as well as someone with normal hearing – hearing thresholds of 20 dB or better in both ears – is said to have hearing loss. Hearing loss may be mild, moderate, severe or profound. It can affect one ear or both ears and leads to difficulty in hearing conversational speech or loud sounds.

Hard of hearing refers to people with hearing loss ranging from mild to severe. People who are hard of hearing usually communicate through spoken language and can benefit from hearing aids, cochlear implants, and other assistive devices as well as captioning.

Deaf people mostly have profound hearing loss, which implies very little or no hearing. They often use sign language for communication.

Causes of hearing loss and deafness

Although these factors can be encountered at different periods across the life span, individuals are most susceptible to their effects during critical periods in life.

Prenatal period

• genetic factors including hereditary and non-hereditary hearing loss
• intrauterine infections – such as rubella and cytomegalovirus infection.

Perinatal period

• birth asphyxia (a lack of oxygen at the time of birth
• hyperbilirubinemia (severe jaundice in the neonatal period)
• low-birth weight 
• other perinatal morbidities and their management.

Childhood and adolescence 

• chronic ear infections (chronic suppurative otitis media)
• collection of fluid in the ear (chronic nonsuppurative otitis media)
• meningitis and other infections.

Adulthood and older age 

• chronic diseases
• otosclerosis
• age-related sensorineural degeneration
• sudden sensorineural hearing loss.

Factors across the life span 

• cerumen impaction (impacted ear wax) 
• trauma to the ear or head
• loud noise/loud sounds
• ototoxic medicines
• work related ototoxic chemicals
• nutritional deficiencies 
• viral infections and other ear conditions
• delayed onset or progressive genetic hearing loss.

The impact of unaddressed hearing loss

When unaddressed, hearing loss impacts many aspects of life at individual level:

• communication and speech;
• social isolation, loneliness and stigma;
• impact on society and economy;effects on years lived with disability (YDLs) and disability adjusted life years (DALYs); and
• education and employment: In developing countries, children with hearing loss and deafness often do not receive schooling. Adults with hearing loss also have a much higher unemployment rate. Among those who are employed, a higher percentage of people with hearing loss are in the lower grades of employment compared with the general workforce.

Many of the causes that lead to hearing loss can be avoided through public health strategies and clinical interventions implemented across the life course.

Prevention of hearing loss is essential throughout the life course, from prenatal and perinatal periods to older age. In children, nearly 60% of hearing loss is due to avoidable causes that can be prevented through implementation of public health measures. Likewise, most common causes of hearing loss in adults, such as exposure to loud sounds and ototoxic medicines, are preventable.

Effective strategies for reducing hearing loss at different stages of the life course include: 

• immunization;  
• good maternal and childcare practices;  
• genetic counselling;  
• identification and management of common ear conditions; 
• occupational hearing conservation programmes for noise and chemical exposure;  
• safe listening strategies for the reduction of exposure to loud sounds in recreational settings; and 
• rational use of medicines to prevent ototoxic hearing loss.  

Identification and management

Early identification of hearing loss and ear diseases is key to effective management.

This requires systematic screening for detection of hearing loss and related ear diseases in those who are most at risk. This includes:

• newborn babies and infants
• pre-school and school-age children
• people exposed to noise or chemicals at work
• people receiving ototoxic medicines
• older adults.

Hearing assessment and ear examination can be conducted in clinical and community settings. Tools such as the hearWHO app and other technology-based solutions make it possible to screen for ear diseases and hearing loss with limited training and resources.  

Once hearing loss is identified, it is essential that it is addressed as early as possible and in an appropriate manner, to mitigate any adverse impact.

Rehabilitation for hearing loss

Rehabilitation helps people with hearing loss to function at their optimum, which means they can be as independent as possible in everyday activities. Specifically, rehabilitation helps them to participate in education, work, recreation and meaningful roles, e.g. in their families or communities–throughout their lives. Interventions for rehabilitation for people with hearing loss include:

• the provision of, and training in the use of, hearing technologies (e.g. hearing aids, cochlear implants and middle ear implants);
• speech and language therapy to enhance perceptive skills and develop communication and linguistic abilities; training in the use of sign language and other means of sensory substitution (e.g. speech reading, use of print on palm, Tadoma, signed communication);
• the provision of hearing assistive technology, and services (e.g. frequency modulation and loop systems, alerting devices, telecommunication devices, captioning services and sign language interpretation); and
• counselling, training and support to enhance engagement in education, work and community life.

WHO response

WHO’s work on ear and hearing care is to promote integrated people-centred ear and hearing care (IPC-EHC).

WHO’s work is guided by the recommendations of the WHO World report on hearing (2021) and the World Health Assembly resolution on prevention of deafness and hearing loss .

WHO’s work includes:

• guiding, assisting and supporting Member States to increase awareness of ear and hearing care  issues;
• facilitating data generation and dissemination of ear and hearing care-related data and information, such as through the World report on hearing ;
• providing technical resources and guidance to facilitate planning and health systems capacity building for ear and hearing care;
• providing guidance to strengthen rehabilitation for people with hearing loss through the Package of interventions for rehabilitation for hearing loss;
• supporting health workforce training in ear and hearing care through the Primary ear and hearing care training resources;
• promoting safe listening to reduce the risk of recreational noise-induced hearing loss through the  WHO Make Listening Safe initiative ; 
• observing and promoting  World Hearing Day  as an annual advocacy event;
• building partnerships to develop strong hearing care programmes, including initiatives for including affordable and accessible ear and hearing care services and hearing aids in service delivery approaches suitable for low-and middle- income countries and cochlear implants; and
• advocating for ear and hearing care through the  World Hearing Forum .

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New Study Links Hearing Loss With Dementia in Older Adults

Findings highlight potential benefit of hearing aid use

A new study led by researchers at the Johns Hopkins Bloomberg School of Public Health found that older adults with greater severity of hearing loss were more likely to have dementia , but the likelihood of dementia was lower among hearing aid users compared to non-users.

The findings, from a nationally representative sample of more than 2,400 older adults, are consistent with prior studies showing that hearing loss might be a contributing factor to dementia risk over time, and that treating hearing loss may lower dementia risk.

The findings are highlighted in a research letter published online January 10 in the Journal of the American Medical Association .

“This study refines what we’ve observed about the link between hearing loss and dementia, and builds support for public health action to improve hearing care access,” says lead author Alison Huang, PhD, MPH, a senior research associate in the Bloomberg School’s Department of Epidemiology and at the Cochlear Center for Hearing and Public Health, also at the Bloomberg School.

Hearing loss is a critical public health issue affecting two-thirds of Americans over 70. The growing understanding that hearing loss might be linked to the risk of dementia, which impacts millions, and other adverse outcomes has called attention to implementing possible strategies to treat hearing loss.

For the new study, Huang and colleagues analyzed a nationally representative dataset from the National Health and Aging Trends Study (NHATS). Funded by the National Institute on Aging, the NHATS has been ongoing since 2011, and uses a nationwide sample of Medicare beneficiaries over age 65, with a focus on the 90-and-over group as well as Black individuals.

The analysis covered 2,413 individuals, about half of whom were over 80 and showed a clear association between severity of hearing loss and dementia. Prevalence of dementia among the participants with moderate/severe hearing loss was 61 percent higher than prevalence among participants who had normal hearing. Hearing aid use was associated with a 32 percent lower prevalence of dementia in the 853 participants who had moderate/severe hearing loss.

The authors note that many past studies were limited in that they relied on in-clinic data collection, leaving out vulnerable populations that did not have the means or capacity to get to a clinic. For their study, the researchers collected data from participants through in-home testing and interviews.   

How hearing loss is linked to dementia isn’t yet clear, and studies point to several possible mechanisms. Huang’s research adds to a body of work by the Cochlear Center for Hearing and Public Health examining the relationship between hearing loss and dementia.

The study authors expect to have a fuller picture of the effect of hearing loss treatment on cognition and dementia from their Aging and Cognitive Health Evaluation in Elders (ACHIEVE) Study. Results from the three-year randomized trial are expected this year.

“Hearing loss and dementia prevalence in older adults in the United States” was co-authored by Alison Huang, Kening Jiang, Frank Lin, Jennifer Deal, and Nicholas Reed.

Support for the research was provided by the National Institute on Aging (K23AG065443, K01AG054693).

Reported Co-Author Disclosures: Nicholas Reed, AuD, serves on the scientific advisory board of Neosensory. Frank Lin, MD, PhD, is a consultant to Frequency Therapeutics and Apple and director of a research center funded in part by a philanthropic gift from Cochlear Ltd to the Johns Hopkins Bloomberg School of Public Health. Lin is also a board member of the nonprofit Access HEARS.

Media contacts: Molly Sheehan at [email protected] and Barbara Benham at [email protected] .

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Association of sudden sensorineural hearing loss with meteorological factors: a time series study in Hefei, China, and a literature review

• Research Article
• Open access
• Published: 17 June 2024

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• Xiao-Bo Li 1 ,
• Yan-Xun Han 2 ,
• Zi-Yue Fu 2 , 3 ,
• Yu-Chen Zhang 2 ,
• Min Fan 2 ,
• Shu-Jia Sang 2 ,
• Xi-Xi Chen 2 ,
• Bing-Yu Liang 2 ,
• Yu-Chen Liu 2 ,
• Peng-Cheng Lu 1 ,
• Hua-Wei Li 4 ,
• Hai-Feng Pan 5 &
• Jian-Ming Yang 1  

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Air pollution can cause disease and has become a major global environmental problem. It is currently believed that air pollution may be related to the progression of SSNHL. As a rapidly developing city in recent years, Hefei has serious air pollution. In order to explore the correlation between meteorological variables and SSNHL admissions, we conducted this study. This study investigated the short-term associations between SSNHL patients admitted to the hospital and Hefei climatic variables. The daily data on SSNHL-related hospital admissions and meteorological variables containing mean temperature (T-mean; °C), diurnal temperature range (DTR; °C), atmospheric pressure (AP; Hp), and relative humidity (RH; %), from 2014 to 2021 (2558 days), were collected. A time-series analysis integrating distributed lag non-linear models and generalized linear models was used. PubMed, Embase, Cochrane Library, and Web of Science databases were searched. Literature published up to August 2023 was reviewed to explore the potential impact mechanisms of meteorological factors on SSNHL. The mechanisms were determined in detail, focusing on wind speed, air pressure, temperature, humidity, and air pollutants. Using a median of 50.00% as a baseline, the effect of exceedingly low T-mean in the single-day hysteresis effect model began at a lag of 8 days (RR = 1.032, 95% CI: 1.001 ~ 1.064). High DTR affected the admission rate for SSNHL on lag 0 day. The significance of the effect was the greatest on that day (RR = 1.054, 95% CI: 1.007 ~ 1.104) and then gradually decreased. High and exceedingly high RH affected the admission rate SSNHL on lag 0 day, and these effects lasted for 8 and 7 days, respectively. There were significant associations between all grades of AP and SSNHL. This is the first study to assess the effect of meteorological variables on SSNHL-related admissions in China using a time-series approach. Long-term exposures to high DTR, RH values, low T-mean values, and all AP grades enhance the incidence of SSNHL in residents. Limiting exposure to extremes of ambient temperature and humidity may reduce the number of SSNHL-related hospital visits in the region. It is advisable to maintain a suitable living environment temperature and avoid extreme temperature fluctuations and high humidity. During periods of high air pollution, it is recommended to stay indoors and refrain from outdoor exercise.

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Air pollution increases the risk of SSNHL: A nested case-control study using meteorological data and national sample cohort data

Long-term exposure to air pollution and the risk of developing sudden sensorineural hearing loss

Air pollutants, seasonal influenza, and acute otitis media in children: a population-based analysis using 22-year hospitalization data

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Introduction

Sudden sensorineural hearing loss (SSNHL) is defined as a hearing loss of at least 30 dB affecting three or more consecutive frequencies over 3 days for unknown reasons. It is commonly, but not always, accompanied by tinnitus and/or vertigo. Every year, five to 27 per 100,000 persons are affected by SSNHL, and approximately 66,000 new cases occur in the “”United States (Chandrasekhar et al. 2019 ). In China, the estimated annual incidence of SSNHL was 19 per 100,000 people (Chandrasekhar et al. 2019 ; Xie et al. 2020 ). Population studies of sudden sensorineural hearing loss have shown the occurrence of this condition in a broad age range with an average age of 50–60 years and no sex preference. The hearing loss is unilateral, with fewer than 5% of instances reporting bilateral involvement (Oh et al. 2007 ). The categories of hearing loss severity include mild, moderate, and severe-profound hearing loss (Nieman and Oh 2020 ). The hearing loss might impact high, low, or all frequencies depending on how it is configured (Moore 2016 ). Approximately 80% of patients have tinnitus, and about 30% experience vertigo, which is indicative of a related peripheral vestibular dysfunction (Nosrati-Zarenoe et al. 2007 ). The sense of having a plugged or numb ear is another typical ailment. Up to 80% of patients report a feeling of ear fullness (Sakata and Kato 2006 ). SSNHL may appear as a standalone issue, as a systemic disease’s presenting symptom, or during an established diagnosis. The complex etiology of SSNHL is still unknown, although risk factors for SSNHL include viral infection, environmental or occupational factors (such as loud noises, heavy metals, and organic solvents), autoimmune diseases, cardiovascular diseases, accidental events, endothelial dysfunction, metabolic diseases, and health habits (such as smoking and alcohol consumption) (Aimoni et al. 2010 ; Chau et al. 2010 ; Ciorba et al. 2010 ; Levy and Amedee 2010 ; Capaccio et al. 2012 ; Choi and Kim 2014 ; Quaranta et al. 2016 ; Umesawa et al. 2017 ; Chen et al. 2019 ; Jeong et al. 2019 ).

During the past 10 years, air pollution has emerged as a significant environmental problem, in both developing and developed nations. Population density, automobile emissions, agriculture, industrial emissions, power plants, and fossil fuel burning have strong positive relationships with air pollutant levels (Liu et al. 2016 ; Gu et al. 2019 ). In recent years, mounting research has suggested that several environmental variables may operate as potential risk factors for the development of SSNHL (Lee et al. 2019b ; Zhang et al. 2021b ; Tsai et al. 2021 ). Additionally, a preliminary report has indicated a seasonal pattern of SSNHL episodes. The results showed that the incidence of SSNHL was lowest in winter and highest in spring (Simani et al. 2022 ). However, no study has been conducted using advanced statistical models to systematically quantify and assess the influence of meteorological variables containing the temperature mean (T-mean), diurnal temperature range (DTR), atmospheric pressure (AP), relative humidity (RH), and wind speed on SSNHL, despite the previously clarified role of ambient temperature in SSNHL. To further explore the relationship between climatic conditions and SSNHL, it is very important to carry out such a systematic quantification and evaluation since it may increase our knowledge of how environmental variables affect SSNHL and provide ideas for enhancing public health.

In order to explore the correlation between meteorological variables and SSNHL admissions, we conducted a time-series analysis to further investigate if these connections varied among subpopulations (groups defined by sex, age, and position of hospital admission). In addition, we collated the previous relevant literature to deeply investigate the possible effects and mechanisms of meteorological factors on SSNHL from several aspects: wind speed, air pressure, temperature, humidity, and air pollutants. This is the first study to comprehensively measure and assess the effect of meteorological variables such as MT, DTR, AP, and RH on SSNHL-related admissions in China using a time-series approach.

Materials and methods

Basic information and overview of the study site.

Hefei, the capital city of Anhui Province, is situated in East China within central Anhui Province (31°52′N, 117°17′E). Hefei experiences a modest annual rainfall of approximately 1000 mm, with prevailing southeasterly winds in spring and summer and northwesterly winds in autumn and winter. The city maintains an annual average temperature of 15.7 °C, with lower temperatures in winter and higher temperatures and humidity in summer due to a thicker inversion layer and slower air flow. These conditions reflect the typical subtropical monsoon climate of eastern China (Chen et al. 2023 ) (Fig.  1 ). According to the 2021 census data, Hefei has a population of 9,369,881, a built-up area of 528.5 km 2 , an urbanization rate (urban population/total population) of 82.28%, and a gross domestic product of 100.4572 billion renminbi (RMB) (China APBoSo. 21 May 2021 edn: https://zwgk.hefei.gov.cn/public/14891/106487817.html , 2019). By selecting Hefei as the focus of this study, the meteorological characteristics of cities in eastern China are accurately represented, allowing for a universal and representative correlation between meteorological variables and SSNHL.

The geographical location of Hefei city

Besides, in recent years, China has experienced rapid economic growth and accelerated urbanization, leading to a significant increase in man-made pollution issues. The Yangtze River Delta region, being the most economically developed coastal special economic zone in China, faces dense cities and highly concentrated air pollution emissions, showcasing distinct regional air pollution characteristics. This area is among the most air-polluted and densely populated regions in China (Feng et al. 2006 ). Hefei, as a representative city in the Yangtze River Delta region, is situated amidst the heavily polluted areas of Beijing-Tianjin-Hebei, Fenwei Plain, and the Yangtze River Delta to the north, west, and east respectively, resulting in severe cross-regional pollution. The primary pollutants contributing to air pollution in Hefei are fine particulate matter (PM2.5) and inhalable particulate matter (PM10), which could potentially impact sudden sensorineural hearing loss (SSNHL). This study not only investigates the correlation between meteorological factors and SSNHL but also delves into the connection between air pollutants and SSNHL in Hefei. Such research can offer a deeper insight into the link between air pollution and disease progression in the Yangtze River Delta region and beyond, serving as a valuable resource for clinical and air quality management practices.

Source and collection of data

The Department of Head and Neck Surgery at the First Affiliated Hospital of Anhui Medical University and the Second Affiliated Hospital of Anhui Medical University, two of the city’s largest public head and neck surgery clinics preferred by local patients with head and neck surgery diseases, provided daily data on hospital admissions (including first admissions and readmissions) for SSNHL in Hefei from 2014 to 2021 (2,558 days). Demographic factors such as age, sex, home address, date of hospital admission, and status of hospital admission were used in the data collection for SSNHL (i.e., first admission or readmission). Hospital admissions records for patients whose demographic details (including sex and age) were not identified or whose residence locations were not in Hefei City were excluded to render the obtained data legitimate and trustworthy. The Ethical Committee of the Anhui Medical University authorized the current research, which was carried out following the Ethical Principles for Medical Research from the Declaration of Helsinki (20,131,220).

The meteorological data were collected from the Hefei Meteorological Bureau and the air pollutant data from Hefei Environmental Monitoring Center. Air pollutant data from Hefei Environmental Monitoring Center contained the daily 8-h highest ozone concentration (O 3 ), particulate matter (PM 2.5 ), carbonic oxide (CO), inhalable particles (PM 10 ), nitrogen dioxide (NO 2 ), and sulfur dioxide (SO 2 ). Meteorological data from Hefei Meteorological Bureau contained RH, daily average temperature, AP, wind speed, daily maximum temperature, and daily minimum temperature, where daily maximum and minimum temperatures were used to calculate the daily average temperature difference.

Statistical analysis

Categorical variables were presented as numbers (%). Continuous variables with a normal distribution were expressed as means (standard deviations, SD) and otherwise as medians (interquartile ranges, IQR). In addition, we removed the strongly correlated variables using the Spearman correlation test, and two variables were considered to be strongly correlated when the test result was greater than 0.7 (Shao et al. 2021 ). Given that environmental exposures are complex and variable, their effects on human health are often non-linear. And the flexibility of generalized additive models is widely used due to their ability to deal well with non-linear points in the environment (Ma et al. 2014 ; Li et al. 2022 ), given that the daily number of hospitalizations for SSNHL in this study is a small probability event and follows a quasi-Poisson distribution. Consistent with previous studies (Gasparrini 2014 ), we used a quasi-Poisson generalized additive model combined with distributed nonlinear lag model (DLNM) to explore the relationship between the admission rate for SSNHL and the climate. The time series model of meteorological factors (MF) was as follows:

where \({\mu }_{t}\) represents the number of daily hospitalizations for SSNHL; \(\alpha\) means the intercept distance; \({MF}_{t,l}\) is the 0 ~  l day lag matrix of MF, β corresponds to the vector coefficients of MF matrix; ns denotes natural cubic spline function; Pollutant represents O 3 , PM 10 , SO 2 , NO 2 , and CO; a natural cubic spline with 8 degrees of freedom per year was used to adjust for seasonality and long-term trend. The effect of weekends and holidays was controlled for by including “DOW” and “Holiday” in the models, respectively.

The evaluation of the degree of fit and freedom of these two models was done with the Akaike information criterion and residual analysis. Based on the incubation period for SSNHL, we reviewed similar literature and determined the lag days as 2 weeks (14 days). We used RR and its 95% CI to depict cumulative and single-day risk results for the admission rate for SSNHL. Finally, the 50th percentile of MF was used as a reference to classify MF into four categories: exceedingly high (95th), high (75th), low (25th), and exceedingly low (5th).

Software usage

The map of Hefei City, Anhui Province, China, was obtained from the software of ArcMap Desktop (10.7.0.10450 version). Descriptive analyses were performed using SPSS 23.0 and the remaining statistical analyses using R software (version 4.1.2). The matching of meteorological models in time series was implemented with “spline” and “DLNM” packages. The criteria for determining bilateral statistical differences were based on a “” p value < 0.05.

Literature review

Two researchers independently searched the Cochrane Database, EMBASE, PubMed, and Web of Science. It was searched using a combination of Medical Subject Heading terms (MeSH), free-text search terms, and Boolean operators. They collected the relevant literature focused on the potential impact mechanisms of meteorological factors on SSNHL until August 2023. The search terms included sudden sensorineural hearing loss, wind speed, air pressure, temperature, humidity, and air pollutants.

The inclusion criteria are research studies that delineated the potential impact mechanisms of meteorological factors on SSNHL. The exclusion criteria are (1) reports of individual cases, evaluations, remarks, and summaries presented at conferences, commentaries, and letters without unique data and (2) data that could not be entirely extracted.

Descriptive summary

The distribution of the daily number of patients with SSNHL, major pollutants, and MFs in Hefei, China, 2014–2021, is shown in Table  1 . We identified a total of 4984 patients with SSNHL over a period of 2558 days, with an average of 1.43 patients with SSNHL per day. Among all patients with SSNHL, there were 1871 instances (51.02%) in men, 1796 (48.98%) in women, 3158 (86.15%) in the 0–65 year age group, and 508 (13.85%) in the ≥ 65 years age group. Among them, the ratio of male to female was about 1:1, and the ratio of young individuals (aged 0–65 years) to older (aged ≥ 65 years) was about 7:1. The T-mean, DTR, RH, AP, and wind speed were 17.40 °C (range: − 5.90 to 35.60 °C), 8.70 (range: 0.60–22.10 °C), 78.00% (range: 33.00–100%), 1012.10 hPA (range: 987.50–1041.00 hPA), and 1.90 m/s (range: 0.30–6.60 m/s), respectively. The average concentrations of the air pollutants PM 2.5 , PM 10 , SO 2 , NO 2 , CO, and O 3 were 44.00 μg/m 3 (PM 2.5 , range: 5.00–351.00 μg/m 3 ), 74.00 μg/m 3 (PM 10 , range: 11.00–413.00 μg/m 3 ), 10.00 μg/m 3 (SO 2 , range: 2.00–58.00 μg/m 3 ), 36.00 μg/m 3 (NO 2 , range: 9.00–134.00 μg/m 3 ), 800.00 μg/m 3 (CO, range: 320.00–2860.00 μg/m 3 ), and 52.00 μg/m 3 (O 3 , range: 4.00–185.00 μg/m 3 ), respectively. Supplementary Fig.  1 presented the temporal trends of meteorological variables and SSNHL outpatient visits in Hefei City during the study period.

Correlation analysis

The outcomes of the Spearman correlation analysis of air pollutants and MF are shown in Fig.  2 A. There were positive correlations between PM 2.5 and PM 10 ( P  < 0.001, r s  = 0.826), and between PM 2.5 and CO ( P  < 0.001, r s  = 0.835). The T-mean and AP were negatively associated with NO 2 , PM 2.5 , SO 2 , PM 10 , and CO and positively associated with O 3 (all P  < 0.001). The DTR was positively associated with NO 2 , PM 2.5 , SO 2 , O 3 , PM 10 , and CO (all P  < 0.001). However, RH was negatively associated with NO 2 , PM 2.5 , SO 2 , PM 10 , CO, and O 3 (all P  < 0.001).

A Spearman’s correlation coefficients for meteorological factors and atmospheric pollutants. B A three-dimensional plot of the relative risk of daily SSNHL vs . T-mean, diurnal temperature range, relative humidity, and atmospheric pressure. C The overall exposure–response association with SSNHL. SSNHL, sudden sensorineural hearing loss

The overall effect of T-mean, DTR, RH, and AP on the admission rate for SSNHL

The exposure–response relationships of the T-mean, DTR, RH, and AP at different values with the admission rate for SSNHL are shown in Fig.  2 B, C. We found a monotonically increasing trend between DTR and SSNHL hospitalization risk. Specifically, the risk of hospitalization in SSNHL increased with increasing DTR values. We also observed that low levels of AP were not associated with the risk of SSNHL admission, but after AP reached a certain level, AP values were positively associated with the risk of SSNHL admission. The association between the T-mean and the admission rate for SSNHL is shown in Table  2 . In the single-day lag, with a median of 50.00% as the reference, extremely low temperature increased the risk of SSNHL admission from lag8 (RR = 1.032, 95% CI: 1.001–1.064) to lag14 (RR = 1.095, 95% CI: 1.03, 1.163), and lag14 had the highest RR. Table 3 records the relationship between DTR and the admission rate for SSNHL. Except for high and exceedingly high DTR, no significant effect was found for the DTR of other grades. Overall, extremely high DTR affected the admission rate for SSNHL on lag 0 day. The significance of the effect was greatest on that day (RR = 1.054, 95% CI: 1.007–1.104) and then gradually decreased. The cumulative risk curve showed a gradual increase in the cumulative risk. In terms of the high RH, the single-day lag association was statistically significant from lag0 to lag7 with the highest RR of SSNHL admission being at lag0 (RR = 1.029, 95%CI: 1.008, 1.050). In the cumulative lag structure, estimated risk effects appeared to be significant from lag0 to lag 0–14. Similar results were observed for the association between extremely high RH and the risk of SSNHL admission (Table  4 ). Interestingly, all grades of AP had significant effects on SSNHL (Table  5 ). The effects of low grades AP were delayed, whereas the effects of high grades AP were immediate.

Stratified analysis by age and sex

Figure  3 shows the stratified analysis results of the “”T-mean according to age and sex. Both hypothermia and hyperthermia had significant effects on SSNHL. At very low DTR, men were affected, and the effect appeared on day 4 of the delay and lasted for 7 days. Both men and women were affected by extremely high DTR, and the effects on women were immediate, whereas men showed significant effects only after a delay of 5 days (Fig.  4 ). At very low RH, men and women as well as the elderly and non-elderly were affected. At extremely high RH, all but the older individuals were affected (Fig.  5 ). Among older individuals and men, SSNHL was almost unaffected by AP. However, under different AP levels, non-elderly women were affected, and the effects were delayed and sustained to different degrees (Fig.  6 ).

Single-day lag effect estimates in SSNHL in T-mean stratified by age and sex. SSNHL, sudden sensorineural hearing loss

Single-day lag effect estimates in SSNHL in diurnal temperature range stratified by age and sex. SSNHL, sudden sensorineural hearing loss

Single-day lag effect estimates in SSNHL in relative humidity stratified by age and sex. SSNHL, sudden sensorineural hearing loss

Single-day lag effect estimates in SSNHL in atmospheric pressure stratified by age and sex. SSNHL, sudden sensorineural hearing loss

Using the originally set search terms, we further read the full text after reviewing the titles, abstracts, and eliminating duplicates, resulting in the inclusion of 15 literatures (Herbert et al. 1987 ; Preyer 1996 ; Danielides et al. 2002 ; Lin et al. 2006 ; Li and Feng 2013 ; Seo et al. 2014 ; Yun et al. 2014 ; Ryu et al. 2017 ; Lee et al. 2019a ; Choi et al. 2019 ; Zhang et al. 2019b ; Tsai et al. 2021 ; Zhang et al. 2021a ; Tang et al. 2022 ; Cheng et al. 2022 ). We deeply investigate the possible effects and mechanisms of meteorological factors on SSNHL from several aspects: wind speed, air pressure, temperature, humidity, and air pollutants (Table  6 ). Database and search strategy are shown in Supplement Table  1 .

Hippocrates proposed that meteorological changes could affect human health in the fifth century (Nastos and Matzarakis 2006 ). And the impact of meteorological factors on acute gouty arthritis (Park et al. 2017 ), rheumatoid arthritis (Azzouzi and Ichchou 2020 ), systemic lupus erythematosus, and Behcet’s disease (Lee et al. 2015 ) has now been demonstrated. As a common emergency in otorhinolaryngology, the etiology of SSNHL is not clear. Now, although there are many studies reporting the seasonal and meteorological effects on the incidence, severity, and prognosis of SSNHL, controversy remains. So, we collated the previous relevant literature to deeply investigate the possible effects and mechanisms of meteorological factors on SSNHL from several aspects: wind speed, air pressure, temperature, humidity, and air pollutants. In addition, a time-series analysis integrating distributed lag non-linear models and generalized linear models was used in order to investigate the short-term associations between SSNHL patients admitted to the hospital and Hefei climatic variables.

Wind speed and atmospheric pressure

Recent viral infection is known to be associated with SSNHL. Several possible mechanisms have been proposed to explain how viral infections lead to SSNHL. The first may be that viral invasion of the cochlear nerve and spiral ganglia through the bloodstream or other routes induces SSNHL (Merchant et al. 2008 ); the second is that under certain conditions, viral reactivation in inner ear tissues initiates the inner ear’s immune response system, activating multiple inflammatory factors, causing endotheliosis and cytokine activation, which can lead to macrothrombi in the inner ear; the third is that viral infection triggers antigenic cross-reactivity in the inner ear, damaging the inner ear (Wilson 1986 ). Seo et al. reported that SSNHL incidence was significantly associated with mean wind speed and maximum wind speed when investigating the association between meteorological factors and SSNHL (Seo et al. 2014 ). Lee (Lee et al. 2019a ) and Yun’s (Yun et al. 2014 ) findings also supported this view, which may be because strong winds increase the spread of the virus and enhance viral susceptibility (Fig.  7 ). Moreover, viral reactivation is based on decreased immune activity, which can be triggered by metabolic changes, physiological stressors, co-infections, cold, psychological stressors, and immunosuppressive states. So strong wind may induce the reactivation of neurotropic virus in spiral ganglion by decreasing immune activity and increase the risk of SSNHL (Seo et al. 2014 ). It has already been reported that higher wind speed may cause idiopathic facial paralysis and vestibular neuritis, and its etiology is similar to that of SSNHL, supporting the association between wind speed and the pathogenesis of SSNHL (Jeon et al. 2013 ).

Potential mechanisms for linkage of wind speed and SSNHL. Strong wind speed can trigger SSNHL from three pathways: enhanced viral transmission, inflammatory immune response, and cross-reactivity. Enhanced viral transmission: In the case of strong wind speed, the virus can invade the spiral ganglion through respiratory transmission and blood transmission, infect the cochlear nerve, and cause hearing damage; inflammatory immune response: strong wind speed can cause elevated levels of IL-6 and TNF and promote the activation and differentiation of CD4T cells, CD8T cells, and B cells, thereby triggering inflammatory responses; cross-reactivity: strong wind speed can trigger cross-reactions and promote IgM production, which binds virus antigens and accidentally binds inner ear antigens and damaging the inner ear. SSNHL, sudden sensorineural hearing loss; IL-6, interleukin 6; TNF, tumor necrosis factor; NF-κB, nuclear factor kappa-B; SIP, steroid receptor coactivator, SRC, SRC-interacting protein; IgM, ImmunoglobulinM; Th17, T helper cell 17; CTL, cytotoxic T lymphocyte; CD4 + , cluster of differentiation 4 plus; CD8 + cluster of differentiation 8 plus

An increase in tympanic membrane tension, which, in turn, results from a variance between middle ear pressure and AP, is thought to be the origin of a feeling of ear fullness in normal ears (Sakata et al. 2009 ). Comprehensive focus is drawn to the processes behind the feeling of ear fullness in acute sensorineural hearing loss, including Meniere’s disease, acute low-tone sensorineural hearing loss, abrupt deafness, and additional hearing-related illnesses. According to Sakata et al. ( 2012 ), there was a noticeable disparity in the minimum sensory threshold for air pressure with negative pressure between the affected and unaffected side of SSNHL patients, suggesting AP to be a key factor in the onset of SSNHL. Herbert suggests that SSNHL is more likely to occur at low pressure, especially when the pressure difference is large (Herbert et al. 1987 ), which is also supported by Preyer ( 1996 ). And he compared patients with complete recovery of hearing thresholds with those who had not yet recovered hearing and found that the former had smaller differences in air pressure and air temperature changes. We hypothesized that this may be due to the lower partial pressure of oxygen during hypobaric pressure, which leads to impaired microcirculation in the inner ear by affecting the production of reactive oxygen species (ROS) and related pathways (Fig.  8 ) (Alde et al. 2023 ). In addition, hyperbaric oxygen treatment is considered a salvage therapy to treat SSNHL, which indicates the effect of AP on SSNHL. However, there is no consensus on the relationship between air pressure and SSNHL, and further verification and discussion are still needed.

Potential mechanisms for linkage of atmospheric pressure and SSNHL. Under the conditions of low air pressure, the partial pressure of oxygen decreases, and hypoxia-induced ROS. ROS depresses levels of NO, induces monocyte invasion, elevates lipid peroxidation, promotes phenotype switching of VSMCs, induces EC dysfunction, precipitates inflammation as well as alters vascular responses and vasotone, which can cause vascular endothelial damage on the one hand, and on the other hand, it can promote Ca 2+ inward flow, consume ATP, inhibit the guanylate cycle, reduce cGMP production, and cause vascular smooth muscle spasm, resulting in microcirculation disorders in the inner ear. SSNHL, sudden sensorineural hearing loss; ROS, reactive oxygen species; ATP, adenosine triphosphate; cGMP, cyclic guanosine monophosphate; O 2 , oxygen; NO, nitrogen; GTP, guanosine triphosphate; PKG, protein kinase G

In contrast to previous studies, our results indicate that all grades of AP have a significant effect on SSNHL. The effects of low grades AP were delayed, whereas the effects of high grades AP were immediate. Besides, we found that AP affected only young women, but not the rest of the population. Given the lack of relevant research in this context, we conjecture that estrogen might play an important role and explain the differences between individuals with and without sensitivity to AP.

Temperature and humidity

The current study with a time-series analysis examined whether the subpopulation-specific (stratified by sex, age, and status of hospital admission) correlations between MF such as T-mean, DTR, AP, and RH, and hospital outpatients for SSNHL varied over the short term and were non-linear and lag-related. We discovered that there was an enhanced positive correlation between DTR and SSNHL risk. This implies that vascular factors may contribute to the development of this subtype of SSNHL. At present, many studies have confirmed the association between cerebrovascular disease and SSNHL. Lin et al. ( 2008 ) found that patients with SSNHL had a significantly higher risk of stroke within 5 years than controls, and stroke patients also had a significantly higher probability of developing SSNHL than non-stroke patients (Kuo et al. 2016 ). For cerebrovascular disease, acute attack of cerebrovascular disease is closely related to temperature, and rapid changes in environmental temperature will dramatically increase the risk of stroke (Lavados et al. 2018 ; Mohammad et al. 2018 ). This suggests that ambient temperature may cause the onset of SSNHL.

There are many studies about the relation between temperature and SSNHL and suggest that the effect of temperature changes on SSNHL is similar to the mechanism by which temperature changes affect cerebrovascular disease (Lee et al. 2019b ; Zhang et al. 2021b ). The blood supply of the cochlea is supplied by the labyrinthine artery, which lacks collateral circulation. When endothelial injury, hypercoagulability, or blood stasis occurs, the cochlear microcirculation may be damaged, resulting in edema, ischemia, and hypoxia of the inner ear tissue, and thus hearing damage (Capaccio et al. 2007 ). Large temperature difference can activate the function of autonomic nerve, enhance the excitability of sympathetic nerve of inner ear, and increase sympathetic excitability of the inner ear. At the same time, it can cause vasospasm, increase platelet count, increase blood viscosity in the inner ear, and even lead to vascular embolism or thrombosis, resulting in microcirculatory disorders in the inner ear and causing SSNHL under the influence of body fluid (Lavados et al. 2018 ). Zhang et al. have found that the characteristics of temperature changes at onset in patients with full-frequency descending SSNHL were similar to those at onset of ischemic stroke, which further supported the pathogenesis discussed earlier: temperature may affect the inner ear microcirculation (Zhang et al. 2019a ). Additionally, the temperature variation may function as a catalyst for the disruption of microcirculation in the inner ear. SSNHL was more easily induced by high DTR to low DTR. The sympathetic nervous system and the renin-angiotensin system are triggered when the body’s ability to adjust to a temperature shift is exceeded (Du et al. 2021 ). This increased secretion of sweat causes the increase of blood viscosity and slow blood stasis, which affects the inner ear microcirculation leading to the pathogenesis (Fig.  9 ).

Potential mechanisms for linkage of temperature and SSNHL. Under high temperatures or large temperature differences, on the one hand, norepinephrine is elevated, which promotes vascular smooth muscle contraction by binding to α1 receptors. Changes in blood flow within the inner ear lead to microcirculatory disorders, causing ischemia, decreased blood oxygen levels, and edema in local tissue cells of the inner ear. This ultimately results in damage to the nerves of the inner ear; on the other hand, high-temperature conditions cause microcirculatory disorders in the inner ear due to the diastole of erector spinae muscles and blood vessels, the increased secretion of sweat, and the increased viscosity of blood, which lead to microcirculatory disorders and damage of the inner ear. SSNHL, sudden sensorineural hearing loss; ATP, adenosine triphosphate; NE, noradrenaline

Our study also supports the findings of previous studies that high temperatures increase the incidence of SSNHL. Besides, we also found that low DTR may reduce the onset of SSNHL in men. Further research into this phenomenon is required to conclude the potential relationship between DTR and SSNHL.

Up to now, there are few studies on the humidity and SSNHL. In our study, RH affected practically all groups. The audiogram configuration of SSNHL can be categorized into five distinct patterns: ascending, descending, flat, profound, and others (Mattox and Simmons 1977 ). According to a prior study, when RH levels were high, individuals were most likely to be ascending patterns. Our results also support this opinion. However, different patterns were proved to be associated with various pathogenetic mechanisms (Kuhn et al. 2011 ). According to a prior study, individuals with ascending patterns had RH levels that were noticeably higher on the day of commencement (Zhang et al. 2021b ). Therefore, we speculate that the large effect of RH may be related to end lymphatic hydrops, although further confirmation is needed.

Air pollution

Industrial production increases the health and economic burden caused by air pollution (Bai et al. 2018 ). Air pollutants include many kinds: NO 2 , NO, CO, PM2.5, etc. Several studies suggest that air pollution could induce SSNHL by many ways including toxic effects, oxidative stress, and inflammatory pathways (Choi et al. 2019 ; Lee et al. 2019a ; Tsai et al. 2021 ; Cheng et al. 2022 ; Tang et al. 2022 ). The possible specific mechanisms of this may be as follows: oxidative stress is dysregulated after inhalation of air pollutants, resulting in increased reactive oxygen species (ROS), which destroys endothelial cells, affects inner ear microcirculation, and induces SSNHL (Lehner et al. 2011 ); when exposed to air pollution, inflammatory cytokine expression is increased, causing an inflammatory response, thereby increasing susceptibility to infection (Hesterberg et al. 2009 ) (Fig.  10 ); in addition, air pollutants are associated with increased cardiovascular morbidity (Dehbi et al. 2017 ). Combined with the above association of SSNHL with cardiovascular disease, it can also be speculated that air pollution may have an impact on SSNHL. And air pollutants may also interact with each other, for example, NO 2 can affect the concentration of NO in the cochlea, and NO, as a signaling molecule between the cochlear space and blood vessels, can lead to changes in cochlear neurotransmission and neuroregulation, which leads to hearing impairment (Heinrich and Helling 2012 ).

Potential mechanisms for linkage of air pollution and SSNHL. Air pollutants damage inner ear epithelial cells by inducing ROS and inflammatory responses, resulting in inner ear microcirculation disorders. ROS: when the concentration of air pollutants is high, ROS will be induced to increase. ROS depresses levels of NO, induces monocyte invasion, elevates lipid peroxidation, promotes phenotype switching of VSMCs, induces EC dysfunction, precipitates inflammation, and alters vascular responses and vasotone, which can cause vascular endothelial damage on the one hand, and on the other hand, it can promote Ca 2+ inward flow, consume ATP, inhibit the guanylate cycle, reduce cGMP production, and cause vascular smooth muscle spasm, resulting in microcirculation disorders in the inner ear. Inflammatory immune response: Air pollutants can cause elevated levels of IL-6 and TNF and promote the activation and differentiation of CD4T cells, CD8T cells, and B cells, thereby triggering inflammatory responses. SSNHL, sudden sensorineural hearing loss; ROS, reactive oxygen species; ATP, adenosine triphosphate; cGMP, cyclic guanosine monophosphate; O 2 , oxygen; NO, nitrogen; GTP, guanosine triphosphate; PKG, protein kinase G; IL-6, interleukin 6; TNF, tumor necrosis factor; NF-κB, nuclear factor kappa-B; SIP, steroid receptor coactivator, Th17, T helper cell 17; CTL, cytotoxic T lymphocyte; CD4 + , cluster of differentiation 4 plus; CD8 + cluster of differentiation 8 plus

Based on the results of previous studies, we analyzed the correlation between air pollutants and MF. The results showed that the T-mean and AP were negatively associated with NO 2 , PM 2.5 , SO 2 , PM 10 , and CO and positively associated with O 3 . The DTR was positively associated with NO 2 , PM 2.5 , SO 2 , O 3 , PM 10 , and CO. However, RH was negatively associated with NO 2 , PM 2.5 , SO 2 , PM 10 , CO, and O 3 .

Limitation and advantage

It is important to note that the present study has some limitations. First, the lack of specific information on the participants’ time spent outside, which can indicate their true degree of exposure to meteorological factors, may result in exposure measurement inaccuracies. Second, since there is a dearth of detailed information, certain possible confounding variables, such as socioeconomic position and family history, could not be adjusted. Finally, since the statistics used in this study were solely from one single city, care should be used when extrapolating the findings of our research to other areas with different climates. More epidemiological studies founded on larger-scale regions and different populations, together with mechanism findings, are urgently required to understand the specific processes responsible for the connections between meteorological variables and SSNHL onset.

Despite these limitations, our study has several advantages. Currently, there are few studies reporting the correlation between meteorological factors and SSNHL. This may be because: (1) SSNHL may appear as a standalone issue, as a systemic disease’s presenting symptom, or during an established diagnosis, which makes it difficult to diagnose, and there are few related reports. As a common disease among the elderly, hearing loss has become a serious public health problem as aging intensifies (Jiang et al. 2023 ). To the best of our knowledge, this is the first study to comprehensively measure and assess the effect of meteorological variables such as MT, DTR, AP, and RH on SSNHL-related admissions in China using a time-series approach. Additionally, the subgroup analysis was further conducted based on sex, age, and status of admission to identify possible vulnerable individuals and obtain a much more accurate estimation of the influence of MF on hospital admission for SSNHL. Additional epidemiological data confirming the effects of meteorological variables on SSNHL could be discovered in our current investigation. Our current investigation discussed the effects of meteorological variables, such as AP, DTR, RH, and T-mean on SSNHL based on additional epidemiological data. Finally, we collated the previous relevant literature to deeply investigate the possible effects and mechanisms of meteorological factors on SSNHL from several aspects: wind speed, air pressure, temperature, humidity, and air pollutants. Based on the results of this study, it is advisable to maintain a suitable living environment temperature and avoid extreme temperature fluctuations and high humidity. During periods of high air pollution, it is recommended to stay indoors and refrain from outdoor exercise. Individuals with underlying conditions like high blood pressure should focus on a balanced diet, and regular exercise and monitor environmental factors such as temperature, humidity, air quality, and air pressure, taking necessary precautions when needed.

This is the first study to comprehensively measure and assess the effect of meteorological variables such as MT, DTR, AP, and RH on SSNHL-related admissions in China using a time-series approach. Our study concludes that exposure to high DTR and RH values, low T-mean values, and all AP grades might increase hospital admissions for SSNHL in areas with humid subtropical monsoon climates, particularly for the first admission. Interestingly, whereas women are vulnerable to all grades of AP exposure, men appear to be more sensitive to low DTR exposure, although older individuals tend to be more sensitive to high RH exposure. Therefore, it is advisable to avoid extreme temperature fluctuations and high humidity. During periods of high air pollution, it is recommended to stay indoors and refrain from outdoor exercise. Individuals with underlying conditions like high blood pressure should focus on a balanced diet, regular exercise, and monitor environmental factors such as temperature, humidity, air quality, and air pressure, taking necessary precautions when needed.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

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The study was supported by funding from the National Natural Science Foundation of China [Grant No.82071055], the Incubation Program of the National Natural Science Foundation of China [Grant No. 2019GMFY06], and the Subject Co-construction project of Anhui Medical University [Grant No.2021lcxk036].

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Yan-Xun Han, Zi-Yue Fu, Yu-Chen Zhang, Min Fan, Shu-Jia Sang, Xi-Xi Chen, Bing-Yu Liang & Yu-Chen Liu

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Xiaobo Li, Yanxun Han, Ziyue Fu: designed the study. Yuchen Zhang and Min Fan: revision of manuscript. Shujia Sang and Xixi Chen: writing the manuscript. Bingyu Liang, Yuchen Liu and Pengcheng Lu: collecting and processing data. Huawei Li, Haifeng Pan, and Jianming Yang: analysis and interpretation of data. Jianming Yang is the sole corresponding author of this manuscript. All authors read and approved the final manuscript.

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Li, XB., Han, YX., Fu, ZY. et al. Association of sudden sensorineural hearing loss with meteorological factors: a time series study in Hefei, China, and a literature review. Environ Sci Pollut Res (2024). https://doi.org/10.1007/s11356-024-33943-1

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Age-Related Hearing Loss (Presbycusis)

On this page:

What is age-related hearing loss?

Why do we lose our hearing as we get older, can i prevent age-related hearing loss, how can i tell if i have a hearing problem, what should i do if i have trouble hearing, what treatments and devices can help, how can my friends and family help me, what research does nidcd support on age-related hearing loss, where can i find more information about age-related hearing loss.

Age-related hearing loss (also called presbycusis, pronounced prez-buh-KYOO-sis) is hearing loss that occurs gradually for many of us as we grow older. It is one of the most common conditions affecting adults as we age. Approximately 15% of American adults (37.5 million) ages 18 and over report some trouble hearing, and about one in three people in the U.S. between the ages of 65 and 74 has hearing loss. Nearly half of those older than 75 have difficulty hearing.

Having trouble hearing can make it hard to understand and follow a doctor's advice, respond to warnings, and hear phones, doorbells, and smoke alarms. Hearing loss can also make it hard to enjoy talking with family and friends, leading to feelings of isolation.

Hearing loss typically occurs in both ears as we age. Because the loss is gradual, you may not realize that you've lost some of your ability to hear.

Many things affect our hearing as we age. For example, changes in the inner ear that can affect hearing are common. Age-related changes in the middle ear and complex changes along the nerve pathways from the ear to the brain can also affect hearing. Long-term exposure to noise and some medical conditions can also play a role. In addition, new research suggests that certain genes make some people more susceptible to hearing loss as they age.

Conditions that are more common in older people, such as high blood pressure and diabetes, are associated with hearing loss. In addition, medications that are toxic to the sensory cells in your ears (some chemotherapy drugs, for example) can cause hearing loss. Less commonly, abnormalities of the middle ear, such as otosclerosis , can worsen hearing with age.

Scientists don't yet know how to prevent age-related hearing loss, but you can protect yourself from noise-induced hearing loss. Potential sources of damaging noises include loud music, headphones/earbuds used at high volume, construction equipment, fireworks, guns, lawn mowers, leaf blowers, and motorcycles. To help safeguard your hearing as you age, avoid loud noises, reduce the amount of time you're exposed to loud sounds, and protect your ears with earplugs or protective earmuffs .

Ask yourself the following questions. If you answer “yes” to two or more of these questions, or “sometimes” to three or more of these questions, you could have hearing loss and should consider having your hearing checked.

• Does a hearing problem cause you difficulty when listening to TV or radio?
• Does a hearing problem cause you difficulty when attending a party?
• Does a hearing problem cause you to feel frustrated when talking to members of your family?
• Does a hearing problem cause you to feel left out when you are with a group of people?
• Does a hearing problem cause you difficulty when visiting friends, relatives, or neighbors?
• Do you feel challenged by a hearing problem?
• Do you feel that any difficulty with your hearing limits or hampers your personal or social life?
• Does a hearing problem cause you to feel uncomfortable when talking to friends?
• Does a hearing problem cause you to avoid groups of people?
• Does a hearing problem cause you to visit friends, relatives, or neighbors less often than you would like?

Adapted from: Cassarly C, Matthews LJ, Simpson AN, Dubno JR. The Revised Hearing Handicap Inventory and Screening Tool Based on Psychometric Reevaluation of the Hearing Handicap Inventories for the Elderly and Adults. Ear Hear. 2020 Jan/Feb;41(1):95-105. doi: 10.1097/AUD.0000000000000746. PMID: 31124792; PMCID: PMC6864238.

If you are concerned about your hearing, you have options for your next steps. Start by learning more about hearing loss. Depending on your symptoms, you might consider over-the-counter hearing aids . If your symptoms are complex, or if you have questions about next steps, consider seeking advice from a hearing health care provider. Primary care physicians, otolaryngologists, and audiologists can be important parts of your hearing health care. Each has a different type of training and expertise:

• A primary care physician is a doctor who practices general medicine and is often our first stop for medical care. This health care provider can refer you to a specialist, if needed, and can also help to determine whether you have other medical conditions that can contribute to hearing loss.
• An otolaryngologist (pronounced oh-toe-lair-in-GAH-luh-jist) is a doctor who specializes in diagnosing and treating diseases of the ear, nose, throat, and neck. An otolaryngologist, often called an ENT, will try to find out why you're having trouble hearing and offer treatment options. Otolaryngologists often work closely with and may refer you to an audiologist.
• An audiologist (pronounced aw-dee-AH-luh-jist) has specialized training in identifying and measuring hearing loss, determining where along the auditory pathway there may be a problem with hearing, and recommending and providing certain hearing loss interventions, such as hearing aids.

Treatment will depend on the severity of your hearing loss, so some treatments or devices will work better for you than others. A number of devices and aids can help when you have hearing loss. Here are the most common ones:

• Hearing aids are electronic instruments you wear in or behind your ear. They make sounds louder. For mild to moderate hearing loss, a new category of hearing aids for adults was established in 2022 by the U.S. Food and Drug Administration. These devices may be purchased over the counter (OTC) from retail or online outlets without seeing a health care professional or getting a hearing test. If you have tried an OTC hearing aid without success or have trouble hearing loud sounds, consult a hearing health professional, because your hearing loss may be more severe.
• Cochlear implants . Cochlear (pronounced COKE-lee-ur) implants are small electronic devices that are surgically implanted in the inner ear and help provide a sense of sound to people who are profoundly deaf or have severe hearing loss.
• Assistive listening devices include telephone and cellphone amplifying devices, apps for use with a smartphone or tablet, and closed-circuit systems (hearing loop systems) in some theaters, auditoriums, and places of worship.

You and your family can work together to make living with hearing loss easier. Here are some things you can do:

• Tell your friends and family about your hearing loss. Explain which listening situations are hard for you.
• Ask your friends and family to face you when they talk so that you can see their expressions and lip movements. This may help you to understand what they’re saying.
• Ask people to speak louder, but not shout. You may need to ask them to slow down when they speak, or to speak more clearly.
• Turn off or turn down the volume of background noise, such as the TV, when you’re trying to have a conversation.
• Be aware of noise around you that can make hearing more difficult. When you go to a restaurant, for example, don't sit near the kitchen or near a band playing music. Ask for seating in a quiet area. Sitting in a booth can help soften or block noise.

NIDCD supports research on the causes of age-related hearing loss, including genes that may make this type of hearing loss more likely. NIDCD-funded scientists are working to understand what happens as we age that interferes with our ability to hear speech in a noisy environment. NIDCD also funds research that explores changes in how the brain processes sound when we lose our hearing. The research to date supports the use of hearing aids to maintain the brain’s sound-processing capabilities.

NIDCD-supported research provided critical data that contributed to the FDA’s decision to make hearing aids available over the counter, without a prescription or health care examination, for adults who believe they have mild to moderate hearing loss. NIDCD continues to support research on ways to make adult hearing health care more accessible and affordable .

NIDCD maintains a directory of organizations providing information on the normal and disordered processes of hearing, balance, taste, smell, voice, speech, and language.

To read more about hearing loss, visit:

• How Do We Hear?
• Do You Need a Hearing Test?
• Over-the-Counter Hearing Aids
• Hearing Aids
• Hearing Aids (FDA)

For more information, contact us at:

NIDCD Information Clearinghouse 1 Communication Avenue Bethesda, MD 20892-3456 Toll-free voice: (800) 241-1044 Toll-free TTY: (800) 241-1055 Email: [email protected]

NIH Pub. No. 23-DC-4235 February 2023

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When The City is Too Loud, How Can We Protect Hearing?

Tagupa, Hyacinth

Hyacinth Tagupa  is a freelance writer with a focus on health care.

In October, Forbes Health published a ranking 1 of U.S. cities according to how much risk they posed to hearing health. The ranking was based on the density of noise-producing establishments in each metro such as bars, restaurants, transportation hubs, construction sites, and sports events. Of the 100 metropolitan areas examined, the Riverside-San Bernardino-Ontario metro in California came out with the most risk, due in large part to its high density of nightclubs, mining sites, and concert venues.

The ranking spotlights the long-standing caution of hearing health advocates that noise in communities adversely impacts the public’s hearing health. What are local governments and health professionals doing about it?

DO BUSIER CITIES MEAN GREATER HEARING LOSS RISK?

For Daniel Fink, MD, founder and chair of The Quiet Coalition, counting the noise-producing sites in a city is not a measure of hearing loss risk.

“Just because these places exist in one city or another is irrelevant. For example, we don’t go to casinos. We don’t work in manufacturing. We don’t go to amusement parks. So the Forbes list has no meaning for me, or really for any one individual living anywhere.”

Fink explained that each person has an individual noise exposure regardless of what kind of establishments are in their town. For example, factors like work, commute, and even podcast listening habits are different from person to person.

He does acknowledge that while risk can’t be quantified just by counting noisy venues, city noise can damage hearing.

“The issue of urban noise causing hearing loss IS an important issue,” Fink stressed.

New York City noise expert Arline Bronzaft, PhD, agrees. “Hearing loss is a physiological disorder. It could happen on one occasion… One loud sound can actually cause harm to our hearing. But in a city, it’s many loud sounds. The cumulative effect over years can impede some of your hearing.”

Samantha Evans, AuD, senior audiologist at University Hospitals in Cleveland, added that common noises in cities contribute to hearing loss.

“Think of the constituents of cities and then think of their recreation and occupations. In Cleveland, we have a large steel mill industry; in Charlotte, N.C., there is a large textile industry. The noise in those industries have brought many people in for hearing evaluations due to difficulty hearing in conversations or in noisy environments. I have evaluated an individual who attended a concert in small night club and stood with their left ear to a speaker. He came into my office reporting his left ear felt full and he had a ringing/buzzing sound in his ear (tinnitus). He was diagnosed with a permanent hearing loss in that ear. It only took one night, one concert, for his hearing levels to decrease.”

ARE NOISE LEVELS IN CITIES SAFE FOR THE PUBLIC?

According to the American Speech-Language-Hearing Association (ASHA) 2 , three factors create risk of noise-induced hearing loss: the loudness of the noise, how close it is to the individual, and for how long the individual is exposed to it.

Safe noise exposure levels are debated across the hearing health care industry, but the ASHA states that hearing loss can result if an individual is exposed to sounds at 85 dBA for over 8 hours at a time. Noise at this decibel is generally akin to that from lawn mowers, busy restaurants, or heavy vehicle traffic. The association also states that noise at 120 dBA upwards—such as from sirens and jackhammers—is not safe for any length of time.

Fink believes that safe levels should be even lower. He has been looking at various noise guidelines and found that commonly accepted U.S. calculations have to be revised downwards. For example, he asserted 3 that the occupational noise recommendations from the National Institute for Occupational Safety and Health were based on “an insensitive measure” of noised-induced hearing loss.

“As I presented at the Acoustical Society of America meeting a year ago, the actual safe noise exposure level to prevent auditory damage may be as low as 55 dBA for a single exposure and an average 55-60 dB for 24 hours. Most cities are certainly noisier than that.”

HOW LOCAL GOVERNMENTS CAN BETTER PROTECT HEARING HEALTH

The Hearing Journal reached out to the public health departments of Riverside County and San Bernardino County, and both pointed to one key issue: hearing health protection is not getting the government support it needs.

“Hearing loss/risk is not a metric tracked by public health at this time. Riverside University Health System does have audiologists to check hearing health but as you probably already know, they are in short supply,” said Janet Zimmerman, public relations director at the Riverside University Health System.

“The services and programs offered by county public health departments are primarily directed and funded by the state, and at this time the state does not support programs or services that focus on populations with hearing impairment,” added Francis Delapaz, communications officer at the San Bernardino County Department of Public Health.

Both counties do have ordinances that aim to control noise. Each of their noise codes has a set of limits for residential, commercial, and industrial zone noise, and for interior and exterior sounds.

But for Bronzaft, local noise ordinances need a major refresh. She has written and spoken extensively about the adverse impact of noise on human health, and currently advocates for New York City to bring its noise legislation up to date.

“We have a noise code. It needs to be updated. It was last updated in 2007 and I was very much involved in the updating,” she told The Hearing Journal . “They’re introducing legislation in New York City like noise cameras… but I have been talking to City Council people. I think we should update the entire code. So I’m advocating that when you have to make some changes piecemeal, you should look at the entire thing.”

For one, according to Bronzaft, noise laws should be based on newer scientific information.

“We now know that 85 dBA was too high a level to set for potential hearing loss. So the information we have now as to what could harm our hearing, how noise can harm our health… really calls for an updating of the noise laws. And that would be true in any city,” she said.

“The other thing that’s key if you’re talking about hearing loss is to educate young people… You need to have schools educating children how important it is to protect their hearing.”

To this end, Bronzaft has helped the NYC Department of Environmental Protection develop an updated Sound and Noise Education Module 4 , which can be included in K-12 learning to teach children about the impact of noise.

Evans agrees and added that childhood education on hearing loss should be tailored to the audience.

“It has to be meaningful for a person, individualized. You won’t get much traction talking about noise-induced hearing loss from farm equipment at a Health Fair in downtown Cleveland.”

She further suggested that cities can also put up educational signage at loud areas like train stops, stadiums, nightclubs, reminding the public of the potential hearing loss risk there. “This would require someone to survey the area to evaluate the decibel level to determine if it poses a risk,” she said.

PROVIDERS’ ROLE IN PROTECTING THE PUBLIC’S HEARING

Besides government initiatives, can audiology professionals help safeguard the public’s hearing health in noisy cities?

Evans believes so. As an example, she cited University Hospitals in Cleveland conducting free hearing screenings at various events, particularly in May, which is National Speech-Language-Hearing Month. They also participate in “Hear in CLE,” a humanitarian effort by audiologists, otolaryngologists, and other providers to provide free hearing health services to underserved communities.

“In addition to reaching out to citizens of urban communities, it’s also appropriate for hearing health care providers to make connections with pediatricians and primary care physicians. These are the providers who serve as a person’s medical home and a place where education can be introduced as well,” said Evans.

Bronzaft and Fink both agree that hearing health care professionals must also participate in lowering hearing loss risk, not just treating it.

“I think hearing health providers must be concerned about [hearing loss] prevention as well,” Bronzaft posited. “I know the role of a doctor is to treat, but… I think research must also be used to benefit the public.”

“The Center for Hearing and Communication is a wonderful example,” she said, referring to a not-for-profit organization that provides comprehensive hearing health services, from hearing testing, to auditory therapies, to family counseling.

“They went into the forefront to develop something called International Noise Awareness Day, because they not only saw that their primary job was to treat hearing loss, but they also saw their goal as trying to prevent further hearing loss,” said Bronzaft. “And remember… they have doctors there that are treating people with hearing loss, but they didn’t stop there. They realized their role was also to educate in terms of prevention.

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Got tinnitus a device that tickles the tongue helps this musician find relief.

Allison Aubrey

After using the Lenire device for an hour each day for 12 weeks, Victoria Banks says her tinnitus is "barely noticeable." David Petrelli/Victoria Banks hide caption

After using the Lenire device for an hour each day for 12 weeks, Victoria Banks says her tinnitus is "barely noticeable."

Imagine if every moment is filled with a high-pitched buzz or ring that you can't turn off.

More than 25 million adults in the U.S., have a condition called tinnitus, according to the American Tinnitus Association. It can be stressful, even panic-inducing and difficult to manage. Dozens of factors can contribute to the onset of tinnitus, including hearing loss, exposure to loud noise or a viral illness.

There's no cure, but there are a range of strategies to reduce the symptoms and make it less bothersome, including hearing aids, mindfulness therapy , and one newer option – a device approved by the FDA to treat tinnitus using electrical stimulation of the tongue.

The device has helped Victoria Banks, a singer and songwriter in Nashville, Tenn., who developed tinnitus about three years ago.

"The noise in my head felt like a bunch of cicadas," Banks says. "It was terrifying." The buzz made it difficult for her to sing and listen to music. "It can be absolutely debilitating," she says.

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Tinnitus bothers millions of americans. here's how to turn down the noise.

Banks tried taking dietary supplements , but those didn't help. She also stepped up exercise, but that didn't bring relief either. Then she read about a device called Lenire, which was approved by the FDA in March 2023. It includes a plastic mouthpiece with stainless steel electrodes that electrically stimulate the tongue. It is the first device of its kind to be approved for tinnitus.

"This had worked for other people, and I thought I'm willing to try anything at this point," Banks recalls.

She sought out audiologist Brian Fligor, who treats severe cases of tinnitus in the Boston area. Fligor was impressed by the results of a clinical trial that found 84% of participants who tried Lenire experienced a significant reduction in symptoms. He became one of the first providers in the U.S. to use the device with his patients. Fligor also served on an advisory panel assembled by the company who developed it.

"A good candidate for this device is somebody who's had tinnitus for at least three months," Fligor says, emphasizing that people should be evaluated first to make sure there's not an underlying medical issue.

Tinnitus often accompanies hearing loss, but Victoria Banks' hearing was fine and she had no other medical issue, so she was a good candidate.

Banks used the device for an hour each day for 12 weeks. During the hour-long sessions, the electrical stimulation "tickles" the tongue, she says. In addition, the device includes a set of headphones that play a series of tones and ocean-wave sounds.

The device works, in part, by shifting the brain's attention away from the buzz. We're wired to focus on important information coming into our brains, Fligor says. Think of it as a spotlight at a show pointed at the most important thing on the stage. "When you have tinnitus and you're frustrated or angry or scared by it, that spotlight gets really strong and focused on the tinnitus," Fligor says.

"It's the combination of what you're feeling through the nerves in your tongue and what you're hearing through your ears happening in synchrony that causes the spotlight in your brain to not be so stuck on the tinnitus," Fligor explains.

A clinical trial found 84% of people who used the device experienced a significant reduction in symptoms. Brian Fligor hide caption

A clinical trial found 84% of people who used the device experienced a significant reduction in symptoms.

"It unsticks your spotlight" and helps desensitize people to the perceived noise that their tinnitus creates, he says.

Banks says the ringing in her ears did not completely disappear, but now it's barely noticeable on most days.

"It's kind of like if I lived near a waterfall and the waterfall was constantly going," she says. Over time, the waterfall sound fades out of consciousness.

"My brain is now focusing on other things," and the buzz is no longer so distracting. She's back to listening to music, writing music, and performing music." I'm doing all of those things," she says.

When the buzz comes back into focus, Banks says a refresher session with the device helps.

A clinical trial found that 84% of people who tried Lenire , saw significant improvements in their condition. To measure changes, the participants took a questionnaire that asked them to rate how much tinnitus was impacting their sleep, sense of control, feelings of well-being and quality of life. After 12 weeks of using the device, participants improved by an average of 14 points.

"Where this device fits into the big picture, is that it's not a cure-all, but it's quickly become my go-to," for people who do not respond to other ways of managing tinnitus, Fligor says.

One down-side is the cost. Banks paid about $4,000 for the Lenire device, and insurance doesn't cover it. She put the expense on her credit card and paid it off gradually.

Fligor hopes that as the evidence of its effectiveness accumulates, insurers will begin to cover it. Despite the cost, more than 80% of participants in the clinical trial said they would recommend the device to a friend with tinnitus.

But, it's unclear how long the benefits last. Clinical trials have only evaluated Lenire over a 1-year period. "How durable are the effects? We don't really know yet," says audiologist Marc Fagelson, the scientific advisory committee chair of the American Tinnitus Association. He says research is promising but there's still more to learn.

Fagelson says the first step he takes with his patients is an evaluation for hearing loss. Research shows that hearing aids can be an effective treatment for tinnitus among people who have both tinnitus and hearing loss, which is much more common among older adults. An estimated one-third of adults 65 years of age and older who have hearing loss, also have tinnitus.

"We do see a lot of patients, even with very mild loss, who benefit from hearing aids," Fagelson says, but in his experience it's about 50-50 in terms of improving tinnitus. Often, he says people with tinnitus need to explore options beyond hearing aids.

Bruce Freeman , a scientist at the University of Pittsburgh Medical Center, says he's benefitted from both hearing aids and Lenire. He was fitted for the device in Ireland where it was developed, before it was available in the U.S.

Freeman agrees that the ringing never truly disappears, but the device has helped him manage the condition. He describes the sounds that play through the device headphones as very calming and "almost hypnotic" and combined with the tongue vibration, it's helped desensitize him to the ring.

Freeman – who is a research scientist – says he's impressed with the results of research, including a study published in Nature, Scientific Reports that points to significant improvements among clinical trial participants with tinnitus.

Freeman experienced a return of his symptoms when he stopped using the device. "Without it the tinnitus got worse," he says. Then, when he resumed use, it improved.

Freeman believes his long-term exposure to noisy instruments in his research laboratory may have played a role in his condition, and also a neck injury from a bicycle accident that fractured his vertebra. "All of those things converged," he says.

Freeman has developed several habits that help keep the high-pitched ring out of his consciousness and maintain good health. "One thing that does wonders is swimming," he says, pointing to the swooshing sound of water in his ears. "That's a form of mindfulness," he explains.

When it comes to the ring of tinnitus, "it comes and goes," Freeman says. For now, it has subsided into the background, he told me with a sense of relief. "The last two years have been great," he says – a combination of the device, hearing aids and the mindfulness that comes from a swim.

This story was edited by Jane Greenhalgh

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Pathogenesis and treatment progress in age-related hearing loss: a literature review

Age-related hearing loss (ARHL) is a progressive sensorineural hearing loss caused by age. The pathogenesis of ARHL is not completely clear at present, but it is closely related to auditory nerve degeneration, metabolic disorders, vitamin deficiency, and genetics, especially mitochondrial DNA damage. With the acceleration of industrialization and urbanization in our country, the impact of environmental noise is increasing, and ARHL has become one of the most important factors affecting the quality of life of the elderly in our country. Therefore, hearing intervention for patients with ARHL plays a crucial role in improving their quality of life. At present, the use of hearing aids and cochlear implants are the main means to treat the daily hearing difficulties and communication difficulties of patients with ARHL. However, in China, due to the economy, the concept of not wanting to treat the elderly, and other reasons, the hearing aid wearing rate compared to developed countries has significant differences. Cochlear implant is another option for patients with presbyacusis, and patients can obtain good hearing and speech recognition rate after surgery. At present, there is no definitive conclusion on whether the quality of life of patients after cochlear implantation has been improved, and this study will be reviewed based on previous relevant reports.

Introduction

Age-related hearing loss (ARHL) is a senile disease with progressive hearing loss gradually occurring with age, mainly manifested by binaural symmetry, slowly progressive sensorineural hearing loss, and eventual severe deafness [ 1 , 2 ]. Generally, the incidence of the disease can be as high as 60% in the elderly aged 65 to 75 years [ 3 ]. ARHL usually has a slow progressive increase, often not noticed at first, with the decline in high-frequency hearing, and the ability to distinguish speech. Patients can hear the sound, but can not hear the content, so words often need to be repeated by others. Then, as hearing becomes more impaired, the speaker is asked to raise his or her voice. ARHL is a multi-factorial disease, such as diseases (hypertension, diabetes), noise, drug toxicity and genetic factors, with complex pathologic mechanisms and characteristics. It is often accompanied by a variety of abnormal manifestations, such as dementia, dull eyes, vision loss, and so on [ 4 - 7 ].

With the aging of society, ARHL has become a major national health problem, which seriously affects the quality of life of the elderly. Therefore, improving the hearing of patients with ARHL can improve communication between the elderly and the outside world, thereby improving their quality of life. Because hearing loss in ARHL is irreversible, drug therapy has little effect on these patients [ 7 - 9 ]. The use of hearing aids is currently one of the main ways to improve communication disorders in ARHL patients, and with the improvement of technology, digital hearing aids have significantly improved the effect compared with traditional hearing aids [ 9 ]. However, according to statistics, the proportion of ARHL patients using hearing aids in China is only 10%-20%.

In recent years, the application of cochlear implantation in ARHL patients has become more common, but whether it is suitable for the treatment of all ARHL patients is still controversial. Current studies have shown that for patients over 60 years old, age growth has almost no impact on speech discrimination after cochlear implantation. Cochlear implantation in the elderly has similar efficacy to young patients, and the impact of organ degradation is not obvious [ 10 , 11 ]. Therefore, from the perspective of safety and quality of life, ARHL implantation of cochlear implants is a relatively good choice.

Previous studies on ARHL were mostly limited to one aspect, such as treatment or quality of life, etc. This study conducted a comprehensive and systematic review from the pathogenesis, treatment and improvement of ARHL quality of life.

Pathogenesis of ARHL

The pathogenesis of ARHL is not a single one. It is the result of a variety of physiological and pathological mechanisms. In addition to the effects of aging, noise and drug toxicity, various senile diseases such as hypertension, hyperglycemia, and hyperlipidemia can cause changes in the osmotic pressure of the labyrinthian lymph fluid of the inner ear, resulting in damage to the structure and function of the cochlea. In addition, roles for ototoxicity, estrogen, and free radicals in the pathogenesis of ARHL have been proposed one after another [ 12 - 14 ]. Especially, more attention has been paid to the role of genetic factors in the pathogenesis of ARHL, especially the factors related to mitochondrial genes that have been found [ 1 , 2 , 15 ].

ARHL with chronic diseases

ARHL is closely related to chronic diseases such as hypertension, diabetes, arteriosclerosis, and hyperlipidemia. Modern anatomy proves that there is no collateral circulation in the auditory artery of the ear, and vascular spasm and embolism are easy to cause ischemia and hypoxia of the inner ear and deafness. The above factors are important factors in the occurrence of vasospasm and embolism. Frisina et al. found that in the elderly population, the hearing function of patients with diabetes is significantly decreased, and aging may lead to slow or blocked blood flow, resulting in hypoperfusion ischemia, labyrinthine microcirculation disorder, and cochlear and vestibular function abnormalities [ 16 ]. Chen Yu et al. found that ARHL patients showed hemorheological abnormalities, mainly reflected in increased whole blood and plasma viscosity, hematocrit, and fibrinogen [ 17 ]. Chai Feng et al. analyzed through clinical observation that hypertension and diabetes can cause different degrees of hearing damage, which is an important factor aggravating ARHL [ 18 ].

ARHL and mitochondrial genes

Mitochondria are common organelles in eukaryotic cells, the main sites for oxidative phosphorylation to produce energy, and they participate in the synthesis of many bioactive substances in the body. In recent years, it has been reported that ARHL is related to mtDNA mutation. Seidman et al.’s animal experiments and human temporal bone sections both found mtDNA deletion in age-related deafness. It has been confirmed that human mtDNA4977bp deletion and mouse mtDNA4834bp deletion are related to ARHL [ 18 ]. In 2002, Zhang et al. found in animal experiments that the absence of mtDNA3867bp in the cochlea might be related to the production of ARH [ 19 ]. In 2006, Wei Xuemei et al. found that the absence of mtDNA4586bp in cochlea spiral tissue and auditory nerve tissue was related to ARHL [ 20 ]. Deletion results in the fusion of the 5th subunit gene of mitochondrial oxidative phosphorylation complex I with the 8th subunit gene of complex V (ATPase), affecting mitochondrial oxidative phosphorylation and ultimately producing bioenergy-deficient cells. Different types of ARHL have a different molecular basis, and not all ARHL patients have mtDNA deletion. mtDNA deletion may be more related to sensorial and vascular ARHL, because there are more mitochondria in the cochlear hair cells and vascular striae [ 21 , 22 ]. mtDNA deletion represents only one aspect of ARHL’s many genetic factors.

Other pathogenesis of ARHL

ARHL with major histocompatibility complex (MHC) Bern-stein showed an increased percentage of patients with MHC B8/DR3 in 14 patients with vascular ARHL, especially A1/B8/DR3 haploids, suggesting a significantly increased incidence of B8/DR3 antigen in patients with vascular ARHL [ 7 , 23 ]. It is speculated that the genes related to this disease may be within or associated with MHC. At the same time, it was pointed out that B8 locus and DR3 locus did not cause disease by themselves, and when the two genes were closely linked, they increased susceptibility to ARHL. The B8/DR8 antigen is associated with changes in immune system activity. This immune dysregulation can lead to the production of protein antibodies, circulating immune complexes, decreased immune complex clearance, and suppression of T cell function [ 5 , 15 ].

ARHL starts earlier in men, (after the age of 30), while in women, it does not start until age 50. This coincides with the menopause transition in most women, when endogenous circulating estrogen levels in the body are declining [ 14 ]. R.K. Shepherd et al. used kanamycin (KA) and the diuretic acetic acid (EA) in the kittens’ age range from 2 to 16 days after birth (DAB), and they found that animals treated with 2-8 DAB sessions showed severe high-frequency hearing loss, and all animals showed bilateral symmetrical hearing loss [ 24 ].

ARHL is the result of both genetic and environmental factors. After years of research, it is believed that ARHL is closely related to noise, smoking, chronic diseases such as hypertension, diabetes, arteriosclerosis, hyperlipidemia, ototoxic drugs, dietary habits, psychosocial factors, and immune function, in addition to the factors mentioned above.

Treatment status of ARHL

Drug therapy.

So far, the pathogenesis of ARHL has not been thoroughly studied, so the research on drug treatment is mostly animal experimental research, and clinical research has not made breakthrough progress. Drug therapy mainly includes anti-oxidation, regulation of mitochondrial function and metabolism, inhibition of apoptosis, regulation of NKCC1, protection of hair cells and anti-inflammation. Polanski et al.’s study compared the efficacy of ginkgo biloba extract, alpha-lipoic acid, VC, VE and placebo, and found that there was no statistical difference in hearing threshold between the observation group and the placebo group [ 25 ].

Hearing aids

At present, hearing aids are one of the main means to improve the daily listening difficulties of ARHL patients and reduce communication barriers. In recent years, digital hearing aids have made major improvements in design and significantly improved in effect, making it easier for ARHL patients to accept hearing aids, and therefore gradually replacing the previous analog hearing aids [ 26 - 28 ]. However, compared to the large number of ARHL patients, the proportion of ARHL patients using hearing aids in China is very small. This proportion is about 10% to 20%, and even some scholars think that it is less than 10%. According to previous literature reports, there are four main reasons for the low wearing rate of hearing aids in China’s ARHL patients: First, Chinese elderly people believe that deafness is a natural decline without intervention. Second, for economic reasons, nearly one-third of patients refuse to wear hearing aids simply because of the price. Third, a considerable number of elderly people worry that hearing aids will aggravate deafness or affect their image. Fourth, some patients cannnot operate and use hearing aids, which is more common in elderly patients [ 5 , 29 ].

Cochlear implant

Cochlear implant is an electronic bionic device. Based on the cochlear electrophysiology principle, the sound is converted into a certain encoded electrical signal by the external speech processor, and the auditory nerve is directly excited by the implanted electrode system in the body to restore or rebuild the hearing function of the deaf.

Cochlear implants have been shown to be an effective treatment for patients with severe and very severe sensorineural hearing loss [ 30 ]. Common concerns regarding cochlear implants in the elderly are the safety of general anesthesia and the impact of degenerative central and peripheral auditory processing in patients with ARHL on implant effectiveness. In this regard, there have been many foreign literature reports in the past decade, and the overall results suggest that for elderly patients ≥65 years old, aging has almost no effect on the discrimination ability of words after cochlear implant. The effect in elderly patients with cochlear implant is close to that of ordinary young patients, and the impact of organ degradation is not obvious [ 30 , 31 ]. In recent years, there have been reports of successful cochlear implantation in ARHL patients ≥60 years old [ 32 - 34 ]. In terms of safety and speech rehabilitation effect, cochlear implants with ARHL have a good prospect.

Cochlear implantation can improve the quality of life of ARHL patients

Although ARHL is not a serious fatal disease, it affects the daily life of elderly patients in their later years. As a special vulnerable group, senile deafness patients have more factors related to their daily life quality and negative emotions. The quality of life and negative mood of patients with senile deafness can be improved by strengthening standardized treatment and improving the disturbances caused by hearing loss and tinnitus.

The study of Zheng Mengmeng et al. showed that the auditory behavior grading, speech intelligibility grading, and speech recognition rate of ARHL patients after cochlear implantation were significantly improved compared with those before surgery [ 34 ]. A number of domestic and foreign studies have confirmed the effectiveness of cochlear implant in improving speech recognition, cognitive function, psychological state and quality of life of ARHL, and the safety of the operation. The complications do not increase with age, and age should not be a limiting factor for cochlear implant in the elderly. Studies by Isabel et al. have shown that hearing and quality of life are improved in older cochlear implant users, with similar effects as in younger people [ 35 ]. Special attention must be paid to the possibility of age-related diseases in the elderly that may increase the risk of surgery.

Liu Ying et al. evaluated 24 patients with ARHL who underwent cochlear implantation. Their study found that the hearing aid threshold of each frequency after cochlear implantation was significantly improved compared with that before surgery. The scores of CAP (auditory behavior grading evaluation), WRS (word list recognition rate evaluation) and SIR (speech intelligibility grading standard) were significantly improved before and after cochlear implantation [ 32 ]. Mosnier et al. compared the cognitive function of 94 patients aged 65-85 years with cochlear implants before, 6 months, and 12 months after surgery, and found that average scores in all cognitive areas improved at 6 months after cochlear implants. The use of cochlear implants can improve the cognitive ability of patients with bi-focused and extremely severe SNHL [ 36 ]. Some scholars have confirmed that the neurocognitive ability of elderly patients with cochlear implant can be improved at 6 months and 12 months after surgery, and the score of quality of life assessment (QLA) can be significantly improved [ 37 ]. This suggests that cochlear implants can significantly improve the independent living ability of elderly patients, and produce obvious economic benefits. In addition, their study showed that the hearing performance and quality of life QLA of older adults (older than 65, 70, and 75 years) improved after cochlear implantation compared to before implantation. Although young individuals have better postoperative recovery than old individuals, this does not negate the judgment that cochlear implant patients are effective for the elderly, because these individuals also have positive effects.

Of course, there are some limitations to this study. First, this study is a review, only a summary of previous relevant studies, and does not propose different treatment views. In addition, the current research on the pathogenesis of ARHL and the improvement of quality of life is still insufficient, and a large number of follow-up studies are still needed to make up for this gap.

Cochlear implantation with ARHL has good development prospects both in terms of safety and speech rehabilitation effect, and can significantly improve the quality of life of ARHL patients.

Disclosure of conflict of interest

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Best Hearing Aids For Profound Hearing Loss Of 2024, According To Audiologists

Medically Reviewed

Profound hearing loss can significantly affect an individual’s quality of life—but effective treatments are available. Our recommendations for the best hearing aids for profound hearing loss may help those with auditory challenges improve their connection to people and the world around them.

To determine the best hearing aids available for profound hearing loss, the Forbes Health editorial team consulted several audiologists from the Forbes Health Advisory Board for product recommendations based on their expertise. Star ratings were solely determined by the editorial team and are based on starting prices, average user ratings and product features that are typically important to hearing aid users. Read on to find out which hearing aids made our list.

Note: Product prices are accurate as of the publication date.

Why You Can Trust Forbes Health

The Forbes Health editorial team prioritizes the accuracy and integrity of the data collected. Our ranking is based on quantitative data and is free from conflicts of interest. We carefully fact check the information featured in our ranking and are committed to producing rankings and supplemental content about hearing health that readers can trust. You can read more about our editorial guidelines and our hearing aids methodology for the rankings below.

• 7 hearing health experts consulted
• 10+ hearing aid brands considered
• 30+ hearing aid models considered
• Best Hearing Aids
• Best OTC Hearing Aids
• Best Affordable Hearing Aids
• Best Hearing Aids For Tinnitus
• Best Hearing Aids For Severe Hearing Loss
• Best Invisible Hearing Aids
• Best Bluetooth Hearing Aids
• Eargo Hearing Aids Review
• Lively Hearing Aids Review
• Jabra Enhance Review

• 360-degree sound & bluetooth enabled
• Nearly invisible with a sleek design
• Delivered straight to your door
• 3 years of convenient, follow-up care from Jabra Enhance's audiology team

Best Hearing Aids for Profound Hearing Loss of 2024

Phonak audéo lumity, starkey genesis ai, widex moment, methodology: how we picked the best hearing aids for profound hearing loss, what is profound hearing loss, treatments for profound hearing loss, how can hearing aids help with profound hearing loss, what to consider in hearing aids made for profound hearing loss, final thoughts, summary: compare the best hearing aids for profound hearing loss, frequently asked questions (faqs), top hearing aids for profound hearing loss.

• Starting price for a pair: $2,498
• Style: Receiver-in-canal (RIC)
• Appropriate for mild, moderate, severe and profound hearing loss
• Battery type: Rechargeable and disposable battery versions available
• Bluetooth compatible
• Trustpilot rating (Phonak): 4.6; BBB rating (Phonak): A+

Phonak’s Audéo Lumity hearing aids focus on improved speech enhancement through Phonak’s unique SmartSpeech technology, according to the company. They feature a versatile fitting range, tap function and great sound quality, says Amy Sarow, Au.D., a Michigan-based audiologist and Forbes Health Advisory Board member.

Users of this device also have the option to “set it and forget it” regarding device settings or tinker with effects to achieve their preferred sound quality for each environment. Phonak is known for managing background noise effectively as well, says Megan Bilodeau, Au.D., a Massachusetts-based audiologist and Forbes Health Advisory Board member.

This hearing aid may also be suitable for people who are active and enjoy spending time outdoors, thanks to its durability and water resistance rating (IP68), meaning the device is waterproof and sweatproof. It comes in both rechargeable and disposable battery versions to suit either preference.

• Available in a variety of fitting options
• Phonak’s Tinnitus Balance program provides customizable tinnitus relief options
• Available in eight colors
• Multiple battery types available
• More affordable than other options on this ranking
• Users with dexterity issues may have difficulty attaching the rechargeable version of this hearing aid to its charging station
• Only available in RIC style
• Accessories can be expensive
• Phonak has a lower BBB customer review rating

“Sonova, the parent company of Phonak, is one of the top five largest global providers of hearing aids. Phonak offers the only completely invisible hearing aid (called the Lyric) and is known for its innovative hearing aid technologies for better sound and hearing, along with advanced streaming and Bluetooth connectivity.”

Read her full review of Phonak hearing aids here.

• Starting price for a pair: $2,798
• Style: Receiver-in-canal (RIC), in-the-ear (ITE), in-the-canal (ITC), completely-in-canal (CIC) and invisible-in-canal (IIC)
• Battery options: Rechargeable
• Trustpilot rating (Starkey): 3.1 stars; BBB rating (Starkey): A+

The Starkey Genesis AI comes recommended by both Dr. Banks and Dr. Bailey due to its artificial intelligence (AI) technology for true-to-life sound quality and myriad health and convenience features. These hearing aids also feature helpful capabilities like music and call streaming to one or both hearing aids and fall detection.

“It’s great for active people who want fitness monitoring and who like to take an active role in tweaking the audio and performance of their hearing aids through the [accompanying] app,” says Dr. Bailey.

These Starkey hearing aids are rechargeable, lasting up to 51 hours on a single charge, according to Dr. Bailey.

• Wide selection of hearing aid styles
• Compatible with Starkey’s full library of wireless accessories
• Accompanying MyStarkey app supports language translation and transcription
• Offers fall detection and health monitoring
• Offers binaural streaming
• Edge Mode+ features AI technology to optimize sound
• Hands-free calling feature isn’t compatible with Android devices
• Wide range of features may not be suitable for users who prefer a simpler device
• Lower Trustpilot rating
• Lower BBB rating for customer reviews

Nicole Gregory

“Starkey hearing aids are available for people with mild to severe hearing loss. Evaluation by an audiologist can help you choose the best Starkey hearing aid for your level of hearing loss, lifestyle and listening environments.”

Read her full review of Starkey hearing aids here.

• Style: Behind-the-ear (BTE), receiver-in-canal (RIC) and in-the-ear (ITE)
• Battery types available: Rechargeable
• Trustpilot rating: 4.2; BBB rating: B-

Widex Moment hearing aids use the company’s Zero Delay and PureSound technology to create a natural sound quality, according to Dr. Sarow. People who enjoy listening to music or who want tinnitus management do especially well with Widex Moment hearing aids, she adds.

Widex Moment hearing aids also feature Bluetooth compatibility and a durable, water-resistant coating. The hearing aids have a 37-hour runtime without streaming, or, for those who enjoy using their hearing aids for music, calls and more, 24 hours of power with eight hours of streaming, according to the company. Plus, the Widex standard charger makes these devices easy to recharge, offering full use from a four-hour charge, or four hours of use from a quick charge of just 30 minutes.

• Smallest rechargeable lithium-ion RIC hearing aid on the market, according to the company
• Promises most natural, least distorted sound experience
• Available in 13 colors
• Powerful charging capabilities
• Multiple charger options available
• Offers accessories specifically for streaming
• Accessory needed for hands-free calling
• Doesn’t stream on all Android devices
• Does not offer disposable batteries option
• Not BBB accredited

Becky Brown

“Many in the hearing health industry believe Widex makes hearing aids with superior sound quality. Its latest model, the Widex Moment hearing aid, uses PureSound technology to provide sound that is clear and natural, according to the company. Innovation in hearing aids has long been the focus at Widex, and the brand is now part of WS Audiology, the third-largest hearing aid company in the world. ”

Read her full review of Widex hearing aids here.

To determine the best hearing aids for profound hearing loss, the Forbes Health editorial team consulted several audiologists on the Forbes Health Advisory Board for specific product recommendations based on their years of experience fitting various hearing aid models for a wide array of patients. Each expert was careful to consider the newest technology available in the hearing aid industry when providing their recommendations, as well as newer brands and the roles they’re playing in this constantly evolving field.

With these recommendations in hand, we dove deeper into the research process, reading reviews from hearing health experts and customers on third-party websites including the Better Business Bureau (BBB), Trustpilot and HearingTracker.com. We also read current, peer-reviewed clinical studies published in the industry’s most respected journals to understand the various causes of hearing loss, how symptoms vary and how evolving hearing aid technology can help those struggling with their hearing health.

The experts’ recommended devices were then ranked based on the following criteria:

• The starting price for a pair of hearing aids (35%)
• The range of hearing loss the devices support (20%)
• How many audiologists recommended them (15%)
• Battery options (10%)
• Bluetooth compatibility (10%)
• Tinnitus management assistance (10%)

Starting price information comes either from ZipHearing or directly from the device manufacturers. All selected hearing aids can be fitted and serviced by audiologists.

Read more about our hearing aids review methodology.

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A person with profound hearing loss is unable to hear speech and hears only very loud sounds, according to the Centers for Disease Control and Prevention (CDC). The hearing loss can occur suddenly or progressively and affect one or both ears. The World Health Organization notes that people with deafness mostly have profound hearing loss, meaning they can hear very little or not at all.

However, legal definitions of deafness vary by nation, says Bill Even, Au.D., communicative and vestibular disorders chief and clinical assistant professor of audiology at UT Southwestern Medical Center in Dallas. “Profound hearing loss generally fits within this definition in most cases,” he says. “However, hearing loss exists on a continuum, and these cutoff points aren’t absolute. A person who fits this legal definition may have some residual hearing when given enough volume or amplification.”

Hearing impairment is graded by loudness sensitivity as measured in decibels, explains Dr. Even. A person with severe hearing loss can hear sounds louder than 60 decibels, but a person with profound hearing loss needs a sound to reach at least 80 decibels before they can detect it, he says.

“Examples of sounds reaching 80 decibels might be similar to that of a hair dryer or an older vacuum cleaner,” says Dr. Even.

A person with profound hearing loss might be unable to hear very loud sounds, such as airplane engines or traffic or fire alarms, he continues. “Many with profound hearing loss need sound to be even louder than 80 decibels, and some sounds might not be heard at all.”

Furthermore, many people have a “sloping” hearing loss, meaning they may have severe hearing loss as it relates to low frequencies and profound hearing loss as it relates to high frequencies, explains Ashley Wenaas, M.D., an otolaryngologist with Memorial Hermann and Texas ENT in Houston.

What Causes Profound Hearing Loss?

Aging is the most common cause of hearing loss, according to Dr. Even. The World Health Organization lists other common causes of hearing loss and deafness:

• Ear-related medical problems, such as otosclerosis (abnormal bone growth in the ear)
• Exposure to loud noise
• Ototoxic (affecting the inner ear or auditory nerve) medications
• Exposure to ototoxic workplace chemicals
• Viral infections
• Chronic diseases
• Head or ear injuries
• Impacted ear wax
• Genetic hearing loss

Chronic conditions, such as high blood pressure and diabetes , can contribute to hearing loss as well.

People with profound hearing loss have very poor hearing and typically need very powerful hearing aids or hearing implants, says Dr. Even. “With or without these amplification options, they often continue to rely on lip-reading or fill in pieces of conversation based on the topic and context.”

As the severity of hearing loss progresses, cochlear implants can be more effective than hearing aids for profound hearing loss, he says, but it can take time to adjust and adapt to them to get the greatest degree of benefit, explains Dr. Even.

Determining whether hearing aids or cochlear implants might better suit your needs depends on your ability to understand speech, says Dr. Wenaas. “When we amplify the sounds to a level where you can hear them, are you able to differentiate the words, or does it all sound garbled?” A hearing health evaluation with an audiologist or hearing health professional is the first step to determining the appropriate treatment for your specific hearing loss.

Previously, hearing aids didn’t provide a great solution for people with profound hearing loss, says Dr. Wenaas. However, hearing aid technology improved tremendously in recent years. Now, hearing aids not only amplify sound, but they do so in a way that more accurately mimics natural sounds, she explains.

“Hearing aids have become extremely sophisticated over the last 10 years,” she says. “The technology that we can now fit inside a tiny hearing aid that sits behind the ear is astounding. I tell my patients to think about the type of cell phone or computer they had 10 years ago compared to what they have now. The advances in hearing aid technology are equally as remarkable.”

• Custom-programmed hearing aids without the markups
• Free lifetime support and next day audiology appointments
• Free upgrades every 18 months with Audicus Premier
• Latest bluetooth technology supports simultaneous connection to 2 devices
• Sleek, barely there models designed for optimal performance and comfort
• 100 Day-Risk Free Trial and Money-Back Guarantee

It’s important to work closely with an audiologist who can tailor hearing aid settings specifically to your lifestyle and the types of sounds you encounter every day, says Dr. Wenaas. “No two people have the same hearing loss, so every hearing aid needs to be individually programmed and curated.”

Hearing aids to treat profound hearing loss are almost always worn behind the ear, says Dr. Even. These hearing aids are more powerful, flexible and customizable for users with profound hearing loss.

“A custom-made earpiece will almost always be necessary to provide enough volume across a wide range of frequencies without acoustic feedback,” he adds.

Fitting hearing aids for profound hearing loss requires skill and expertise, notes Dr. Even. “Try to stay positive and committed to the process,” he advises. “Work with your audiologist to develop some realistic and achievable expectations, as well as to track your progress.”

Our top pick for the best hearing aid for profound hearing loss is Phonak Audéo Lumity. Our audiologists who recommended Phonak applaud the product’s sound quality, versatile fitting range, durability and ability to handle background noise.

Our other top picks for hearing aids for profound hearing loss include Starkey Genesis AI and Widex Moment.

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Is profound hearing loss worse than severe?

Yes, severe hearing loss is defined as only being able to hear sounds louder than 60 decibels while profound hearing loss is defined as only being able to hear sounds louder than 80 decibels.

Is profound hearing loss considered deaf?

Profound hearing loss and deafness are often used synonymously. Profound hearing loss describes a level of hearing loss that makes it impossible for the person to perceive usable sound without some type of intervention.

What percentage of hearing loss is considered profound?

Of the estimated 1.57 billion people worldwide who navigated hearing loss in 2019, 10% to 15% of them experienced complete hearing loss, according to research from the World Health Organization [2] Hearing loss prevalence and years lived with disability, 1990–2019: findings from the Global Burden of Disease Study 2019 . World Health Organization. Accessed 1/27/2023. .

• Hearing Loss in Older Adults. National Institute on Deafness and Other Communication Disorders. Accessed 1/6/2023.
• Hearing loss prevalence and years lived with disability, 1990–2019: findings from the Global Burden of Disease Study 2019. World Health Organization. Accessed 1/27/2023.
• Deafness and Hearing Loss. World Health Organization. Accessed 1/6/2023.
• Understanding Hearing Loss. Centers for Disease Control and Prevention. Accessed 1/6/2023.
• Age Related Hearing Loss. National Institute on Deafness and Other Hearing Disorders. Accessed 1/6/2023.
• Goman, AM, Lin FR. Prevalence of Hearing Loss by Severity in the United States. Am J Public Health. 2016;106(10):1820–1822.
• Types of Hearing Loss. Centers for Disease Control and Prevention. Accessed 1/6/2023.
• Hearing Loss and Older Adults. National Institute on Deafness and Other Communication Disorders. Accessed 1/6/2023.

Next Up In Hearing Aids

• Best Over-the-Counter (OTC) Hearing Aids
• Best Hearing Aids For Seniors

Information provided on Forbes Health is for educational purposes only. Your health and wellness is unique to you, and the products and services we review may not be right for your circumstances. We do not offer individual medical advice, diagnosis or treatment plans. For personal advice, please consult with a medical professional.

Forbes Health adheres to strict editorial integrity standards. To the best of our knowledge, all content is accurate as of the date posted, though offers contained herein may no longer be available. The opinions expressed are the author’s alone and have not been provided, approved or otherwise endorsed by our advertisers.

Based in Tampa, Florida, Virginia Pelley is a former women's magazine editor who has written health and fitness content for Men's Journal, Cosmopolitan magazine, the Chicago Tribune, WashingtonPost.com, Greatist and Beachbody. She has also written for MarieClaire.com, TheAtlantic.com, Glamour magazine, Fatherly and VICE. A devotee of YouTube fitness videos, she also enjoys stand-up paddleboarding and exploring the natural springs of her adopted state.

Alena is a professional writer, editor and manager with a lifelong passion for helping others live well. She is also a registered yoga teacher (RYT-200) and a functional medicine certified health coach. She brings more than a decade of media experience to Forbes Health, with a keen focus on building content strategy, ensuring top content quality and empowering readers to make the best health and wellness decisions for themselves.

Lindsey Banks is a Florida-licensed audiologist and fellow of the American Academy of Audiology. She currently provides tinnitus and hearing loss support for patients online at Dr. Hearing Loss. She previously managed other audiologists at Center for Sight, a large ophthalmology-owned private practice, and provided patient care through hearing diagnostic testing, hearing aid fittings and tinnitus counseling. Banks also previously served as an audiology extern for the Charlie Norwood VA Medical Center and a clinical and dispensing audiologist and tinnitus specialist for ENT Hearing Associates of South Florida. She spent six years helping grow EverydayHearing.com as a medical reviewer and consultant as well.

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June 17, 2024

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Northern Territory First Nations children receive effective vaccine to reduce infection-induced hearing loss

by Menzies School of Health Research

A study led by Menzies School of Health Research has uncovered that Northern Territory (NT) First Nations children aged 12–36 months have access to an effective vaccine that could prevent hearing loss.

Published in PLOS Medicine , this five-year study looked to uncover which type of pneumococcal conjugate vaccine (PCV), +P or +S, could best reduce debilitating hearing loss caused by chronic otitis media (middle ear infection).

The +P vaccine (known as PCV13) is the vaccine currently provided to children in the NT, and the study found the group who received +P had better hearing than those who in the +S vaccine (known as PHiD-CV10) group. The difference in hearing loss between the two vaccine groups was found to be 20% (but due to the small sample size , the real difference is likely to be between 1–37%).

Due to vaccine formulations and the bacterial make-up of otitis media, it was expected that the +S vaccine would provide better protection against hearing loss. These findings are crucial to helping guide research, policy and practice, particularly as new vaccine formulations become available.

This research moves one step closer to tackling the impacts of otitis media, where Australian First Nations children have the highest reported rates of otitis media in the world.

These studies, independent of the pharmaceutical industry , looked at the role vaccines can have in preventing hearing loss, helping to address the life-long and debilitating effects of otitis media.

Lead author of the study, Professor Amanda Leach AM, has dedicated her career to tackling otitis media, one of Australia's greatest health challenges.

"Almost every Australian First Nations child living in remote regions of the Northern Territory experiences chronic otitis media in their early years of life. It is crucial that this illness is prevented or treated early, to reduce hearing loss, and subsequent impacts on learning and development.

"These studies are vital in ensuring that vaccines are best meeting the needs of high-risk populations and strive to achieve better health outcomes for First Nations children.

"We also thank the First Nations families who participated in this study. We greatly value their commitment to improving the health and education outcomes for their children," said Prof. Leach.

Senior author of the study and Menzies Senior Principal Research Fellow, Professor Peter Morris, said, "All young children should be able to hear, listen, speak and learn to communicate during their early years of life. However, due to the devastating impacts of chronic otitis media , First Nations children experience life-long disadvantage due to this illness.

"The results of this study are extremely helpful. Many people thought that the +S vaccine would be better, but the prevalence of moderate hearing loss halved and normal hearing doubled in those who received the +P vaccine (PVC13) when compared to the +S group. This trend continued at each six month follow up, until the child reached 3 years of age, but with a smaller difference.

"We welcome the opportunity to further evaluate the impact of these vaccines. Clinical trials are the best way to understand their effectiveness and to help stop this preventable disease in its tracks."

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