The physiological bases and perceptual consequences of 'hidden' noise-induced hearing loss

Lead Research Organisation: University of Manchester
Department Name: School of Health Sciences

Abstract

Noise exposure is the main cause of preventable hearing loss worldwide. Noise exposure occurs in the workplace, such as in noisy factories, and recreationally, through the use of personal music players and attendance at nightclubs and live music events. Hearing loss is usually diagnosed using pure tone audiometry, which measures the sensitivity of the ear to quiet sounds by determining the levels of tones that can just be heard at several test frequencies. Until recently, it had been assumed that hearing loss results mainly from damage to the sensory hair cells in the cochlea, the part of the ear that converts acoustic vibrations into electrical impulses in the auditory nerve. However, recent results from animal studies suggest that moderate noise exposure can cause substantial damage to the auditory nerve, even when the hair cells are unaffected. Crucially, the results suggest that such damage does not affect sensitivity to quiet sounds, and hence is not detectable by pure tone audiometry. Hearing loss that is not detectable by conventional audiometry is sometimes called "hidden" hearing loss.

Auditory nerve damage degrades the information that is carried by the nerve from the ear to the brain. Some studies suggest that people with a history of noise exposure, but with normal hearing sensitivity as measured by pure tone audiometry, have problems with sound discrimination, including understanding speech in noisy environments. However, to date no direct link has been made between the physiological results and the perceptual deficits. It is also possible that damage to the auditory nerve leads to tinnitus (perception of sound in the absence of external sound: "ringing in the ear") and hyperacusis (diminished tolerance of moderate-to-high level sounds).

Hidden hearing loss is potentially a huge problem. Substantial numbers of people, probably millions in the UK alone, are routinely exposed to occupational and/or recreational noise levels similar to, or greater than, those used in the animal studies. A large UK study found that one in seven adults aged 17-30 reported "great difficulty" hearing speech in noisy backgrounds, while only one in fifty had impaired sensitivity as measured by pure tone audiometry. Hidden loss leads to a reduction in quality of life, and is likely to be predictive of more severe hearing loss in old age. Hence, hidden hearing loss is a major public health issue, which demands a comprehensive investigation.

Our programme is far-reaching and ambitious, involving three internationally renowned institutions across the UK and US, and a wide range of scientific methodologies. These include physiological and perceptual measures on both animals and humans. Our approach is to use overlapping methodologies across the animal and human studies so that we can understand the perceptual deficits experienced by humans in terms of the underlying physiological mechanisms. We will estimate the prevalence of hidden loss in young adults, and the impact of hidden loss on everyday tasks such as speech and music perception. We will also determine how hidden loss is related to tinnitus and hyperacusis. Finally, we will use our results to develop a sensitive diagnostic test that can be used to detect hidden loss, hence allowing the detection of hearing loss that is undetected by current clinical procedures.

Our research is expected to lead to a number of benefits. A diagnostic test for hidden loss in the clinic, and for monitoring the hearing of workers, will allow identification of at-risk individuals, and provision of personalised healthcare advice, regarding, for example, ways to reduce noise exposure. Our research could also result in a reduction in legal noise exposure limits. These measures will help prevent hidden loss, improve patient outcomes, and reduce usage of healthcare resources. Longer-term, there may be the possibility of reversing auditory nerve damage by replacing lost nerve fibres using stem cells.

Technical Summary

Noise exposure is the main cause of preventable hearing loss worldwide. Dramatic results from recent animal experiments suggest that moderate noise exposure can cause substantial permanent damage to the auditory nerve that is not detected by standard hearing tests. A large number of people, probably millions in the UK alone, are exposed to occupational and recreational noise levels similar to, or greater than, those used in the animal experiments. There is some evidence that people with a history of noise exposure, but with normal hearing as measured by pure tone audiometry, have perceptual deficits that include tasks such as hearing speech in noisy backgrounds. This "hidden" loss may also be associated with tinnitus and hyperacusis. Together, these deficits lead to a reduced quality of life for the individuals concerned. It is vital that we understand the mechanisms and consequences of hidden hearing loss so that we can:

1. Adequately assess hearing ability, and provide appropriate treatments
2. Identify at-risk individuals and provide personalised healthcare advice to prevent further damage
3. Re-evaluate EU noise-exposure regulations

Our proposal is far-reaching and multidisciplinary, combining animal histology, neurophysiology, electrophysiology, and psychophysics, with human electrophysiology, psychophysics, and neuroimaging. By using overlapping methodologies across the animal and human experiments, it will be possible to make inferences regarding the physiological bases of noise-induced damage in the human auditory system; information that will be vital for the diagnosis and treatment of hidden hearing loss. The animal noise-exposure experiments will also be invaluable in the determination of safe noise levels for humans. The results will allow us to identify the perceptual effects of hidden damage, and provide a diagnostic test. We will also provide an estimate of the prevalence of this type of loss in young adults, and the risk factors involved.

Planned Impact

Beneficiaries of the research include:

1. Individuals at risk through noise exposure.

These individuals will benefit from the diagnostic test, allowing more accurate and sensitive diagnosis of hearing loss, and personalised healthcare advice, leading to prevention of further loss and improved quality of life (~5-10 yr impact).

Accurate diagnosis and an understanding of the physiological mechanisms of hidden loss will pave the way for potential treatments such as noise reduction techniques in hearing aids (~10-20 year impact) and stem cell therapies (~15-30 year impact).

2. Workers at risk through occupational noise exposure.

These individuals will also benefit from the diagnostic test, allowing more sensitive health surveillance. There is also likely to be a re-evaluation of noise exposure regulations. Both outcomes will contribute to prevention of further loss (~5-10 yr impact).

3. Healthcare providers / clinicians

Benefit through improved diagnosis of hearing disorders, and ability to offer appropriate advice and counselling to those that report difficulties hearing in noisy situations but are currently told that they have "normal" hearing (~5-10 yr impact).

4. Policy makers concerned with noise exposure regulations and health surveillance in the workplace.

Benefit with more accurate information regarding the impact of environmental noise (~5-10 yr impact).

5. Industries and insurance companies

Benefit through more appropriate noise-exposure / surveillance regulations, and reduction in insurance claims for hearing loss (~10-15 year impact).

6. UK economy

Prevention of hearing damage will reduce usage of healthcare resources (~10-15 year impact).

Publications

10 25 50
 
Description NIH workshop on cochlear synpatopathy, leading to recommendations for future research initiatives.
Geographic Reach North America 
Policy Influence Type Membership of a guideline committee
URL http://www.nidcd.nih.gov/funding/programs/Pages/synaptopathy-summary.aspx
 
Description Article on Hidden Hearing Loss in Occupational Health at Work Journal 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Article on Hidden Hearing Loss due to occupational noise exposure
Year(s) Of Engagement Activity 2016
URL http://www.atworkpartnership.co.uk/occupationalhealthatwork.php/issue/12_5/article/353/?s=1
 
Description BBC East Midlands Today news article for SPMIC launch 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Media (as a channel to the public)
Results and Impact TV news article around launch of the Sir Peter Mansfield Imaging Centre where the study was highlighted as a research area that will benefit from new equipment installation
Year(s) Of Engagement Activity 2017
 
Description BBC East Midlands Today news article for tinnitus awareness week 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Media (as a channel to the public)
Results and Impact TV news article based around noise exposure and tinnitus and also to assist recruitment to the study - anyone who got in touch with the BBC was asked to e-mail me directly
Year(s) Of Engagement Activity 2017
 
Description BBC Nottingham radio item 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Media (as a channel to the public)
Results and Impact radio interview based around noise exposure and tinnitus, asking interested parties to get in touch through website or twitter
Year(s) Of Engagement Activity 2017
 
Description BBC1: Health: Truth or Scare 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Interview and demonstration on dangers of recreational noise exposure
Year(s) Of Engagement Activity 2017
 
Description BBC1: Watchdog 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Interview and demonstration on dangers of noise exposure from household appliances
Year(s) Of Engagement Activity 2017
 
Description British Academy of Audiology Regional Study Day 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Talk on hidden hearing loss to clinicians
Year(s) Of Engagement Activity 2016
 
Description British Science Association Public Lecture Series "I can see what you hear" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A public lecture on neuroimaging and auditory neuroscience followed by questions and debate
Year(s) Of Engagement Activity 2017
URL https://www.nottingham.ac.uk/physics/outreach/science-public-lectures.aspx
 
Description British Science Association SciBar "watching your brain" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A public lecture given in a pub on neuroimaging and auditory neuroscience followed by questions and debate
Year(s) Of Engagement Activity 2017
URL https://www.leftlion.co.uk/read/2017/august/nottingham-scibar-july-nottinghamshire-bsa-british-scien...
 
Description British Society of Audiology Christmas Special eSeminar on Hidden Hearing Loss 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact On-line seiminar on Hidden Hearing Loss, covering effects of noise exposure and ageing.
Year(s) Of Engagement Activity 2015
URL https://connect.sonova.com/p9n0ylpvhz2/
 
Description Derby human biology society "I can see what you hear" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A public lecture on neuroimaging and auditory neuroscience followed by questions and debate with many students saying they were inspired to consider the field
Year(s) Of Engagement Activity 2017
 
Description Interviewed for Mail Online article on Hidden Hearing Loss 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact 374 comments online as of 7/10/15, and several email enquiries

Requests to particpate in future research
Year(s) Of Engagement Activity 2015
URL http://www.dailymail.co.uk/health/article-3217425/Is-real-reason-t-hear-conversation-round-dinner-ta...
 
Description Interviewed for Mail Online article on Hidden Hearing Loss and dangers of noise exposure 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Comments, online discussions

None
Year(s) Of Engagement Activity 2015
URL http://www.dailymail.co.uk/health/article-3051533/Are-victim-HIDDEN-hearing-loss-listen-radio-maximu...
 
Description Invited Presentation at International Symposium on Auditory and Audiological Research, Denmark 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk sparked questions and discussion

N/A
Year(s) Of Engagement Activity 2015
URL http://www.isaar.eu/
 
Description Invited presentation at 12th European Federation of Audiology Societies, Istanbul 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk sparked questions and discussions

N/A
Year(s) Of Engagement Activity 2015
URL http://efas2015.eu/scientific_programme.php
 
Description Invited talk at Amplifon Centre for Research and Studies Conference International Conference, Valencia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk on hidden hearing loss to practitioners and industry
Year(s) Of Engagement Activity 2016
 
Description Keynote presentation at International Hearing Aid Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Talk on hidden hearing loss
Year(s) Of Engagement Activity 2016
 
Description Keynote to British Academy of Audiology 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Talk on cochlear synaptopathy, describing our recent findings
Year(s) Of Engagement Activity 2017
 
Description Keynote to Canadian Academy of Audiology 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk on cochlear synaptopathy, describing our recent findings
Year(s) Of Engagement Activity 2017
 
Description Poster at Lancet Neurology Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Poster on diabetes and hidden auditory deficits
Year(s) Of Engagement Activity 2016
 
Description Presentation in Science Tent at Secret Garden Party festival 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Approx 60 festival goers attended talk on hearing and dangers of noise expsoure. There were several questions on topics such as hearing protection and tinnitus.

N/A
Year(s) Of Engagement Activity 2014
 
Description Radio interview for smooth and capital FM 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Media (as a channel to the public)
Results and Impact radio interview based around the damages of listening to mp3 players too loud
Year(s) Of Engagement Activity 2017
 
Description Soapbox science 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Soapbox Science is a novel public outreach platform for promoting women scientists and the science they do. Events transform public areas into an arena for public learning and scientific debate; they follow the format of London Hyde Park's Speaker's Corner.
Year(s) Of Engagement Activity 2017
URL http://soapboxscience.org/soapbox-art-science-lincoln-2017/
 
Description Talk at Starkey Laboratories 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Talk on diagnosis of hidden hearing loss to an industrial research laboratory
Year(s) Of Engagement Activity 2016
 
Description Talk on Hidden Hearing Loss to Specsavers PAC 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presentation on hidden hearing loss at the Specsavers Professional Advancement Conference
Year(s) Of Engagement Activity 2018