View source for Medicine:Hearing loss

{{short description|Partial or total inability to hear}}
{{Infobox medical condition (new)
| name          = Hearing loss
| image         = International Symbol for Deafness.svg
| alt           = A stylized white ear, with two white bars surrounding it, on a blue background.
| caption       = 
| field         = Otorhinolaryngology, [[Physics:Audiology|audiology]]
| symptoms      = Decreased ability to hear
| complications = [[Social:Social isolation|Social isolation]],<ref name=WHO2015/> [[Medicine:Dementia|dementia]]
| onset         = 
| duration      = 
| types         = Conductive, sensorineural, and mixed hearing loss, [[Medicine:Cortical deafness|central auditory dysfunction]]<ref name=Sm2014/>
| causes        = [[Biology:Genetics|Genetics]], aging, exposure to noise, some [[Medicine:Infection|infection]]s, birth complications, trauma to the ear, certain medications or toxins<ref name=WHO2015/>
| risks         = 
| diagnosis     = Hearing tests
| differential  = 
| prevention    = [[Biology:Immunization|Immunization]], proper care around [[Medicine:Pregnancy|pregnancy]], avoiding loud noise, avoiding certain medications<ref name=WHO2015/>
| treatment     = Hearing aids, [[Social:Sign language|sign language]], cochlear implants, [[Engineering:Closed captioning|closed captioning]], [[Engineering:Subtitles|subtitles]]<ref name=WHO2015/>
| medication    = 
| prognosis     = 
| frequency     = 1.33 billion / 18.5% (2015)<ref name=GBD2015Pre>{{cite journal | title = Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015 | journal = Lancet | volume = 388 | issue = 10053 | pages = 1545–1602 | date = October 2016 | pmid = 27733282 | pmc = 5055577 | doi = 10.1016/S0140-6736(16)31678-6 | last1 = Vos | first1 = Theo | last2 = Allen | first2 = Christine | last3 = Arora | first3 = Megha | last4 = Barber | first4 = Ryan M. | last5 = Bhutta | first5 = Zulfiqar A. | last6 = Brown | first6 = Alexandria | last7 = Carter | first7 = Austin | last8 = Casey | first8 = Daniel C. | last9 = Charlson | first9 = Fiona J. | last10 = Chen | first10 = Alan Z. | last11 = Coggeshall | first11 = Megan | last12 = Cornaby | first12 = Leslie | last13 = Dandona | first13 = Lalit | last14 = Dicker | first14 = Daniel J. | last15 = Dilegge | first15 = Tina | last16 = Erskine | first16 = Holly E. | last17 = Ferrari | first17 = Alize J. | last18 = Fitzmaurice | first18 = Christina | last19 = Fleming | first19 = Tom | last20 = Forouzanfar | first20 = Mohammad H. | last21 = Fullman | first21 = Nancy | last22 = Gething | first22 = Peter W. | last23 = Goldberg | first23 = Ellen M. | last24 = Graetz | first24 = Nicholas | last25 = Haagsma | first25 = Juanita A. | last26 = Hay | first26 = Simon I. | last27 = Johnson | first27 = Catherine O. | last28 = Kassebaum | first28 = Nicholas J. | last29 = Kawashima | first29 = Toana | last30 = Kemmer | first30 = Laura }}</ref>
| deaths        = 
| image_size    = 200px
}}
<!-- Definition and symptoms -->
'''Hearing loss''' is a partial or total inability to [[Physics:Hearing|hear]].<ref name="Britannica">{{cite encyclopedia | year=2011 | title=Deafness | encyclopedia=Encyclopædia Britannica Online | publisher=Encyclopædia Britannica Inc. | url=https://www.britannica.com/EBchecked/topic/154327/deafness | access-date=2012-02-22 | url-status=live | archive-url=https://web.archive.org/web/20120625153552/https://www.britannica.com/EBchecked/topic/154327/deafness | archive-date=2012-06-25 }}</ref> Hearing loss may be present at birth or acquired at any time afterwards.<ref name=":4">{{cite web|date=2020-03-01|title=Deafness and hearing loss|url=https://www.who.int/news-room/fact-sheets/detail/deafness-and-hearing-loss|access-date=2020-07-13|website=World Health Organization|language=en}}</ref><ref>{{cite web|title=Hearing Loss at Birth (Congenital Hearing Loss)|url=https://www.asha.org/public/hearing/congenital-hearing-loss/|access-date=2020-07-13|website=American Speech-Language-Hearing Association|language=en}}</ref>  Hearing loss may occur in one or both ears.<ref name=WHO2015/> In children, hearing problems can affect the ability to [[Social:Language acquisition|acquire]] spoken [[Social:Language|language]], and in adults it can create difficulties with social interaction and at work.<ref name=Las2014>{{cite journal | vauthors = Lasak JM, Allen P, McVay T, Lewis D | title = Hearing loss: diagnosis and management | journal = Primary Care | volume = 41 | issue = 1 | pages = 19–31 | date = March 2014 | pmid = 24439878 | doi = 10.1016/j.pop.2013.10.003 }}</ref> Hearing loss can be temporary or permanent. [[Medicine:Presbycusis|Hearing loss related to age]] usually affects both ears and is due to cochlear hair cell loss.<ref name=Sch2017>{{cite journal|last1=Schilder|first1=Anne Gm|last2=Chong|first2=Lee Yee|last3=Ftouh|first3=Saoussen|last4=Burton|first4=Martin J.|date=2017|title=Bilateral versus unilateral hearing aids for bilateral hearing impairment in adults|journal=The Cochrane Database of Systematic Reviews|volume=2017|issue=12|pages=CD012665|doi=10.1002/14651858.CD012665.pub2|issn=1469-493X|pmc=6486194|pmid=29256573}}</ref> In some people, particularly older people, hearing loss can result in loneliness.<ref name=WHO2015/>

<!-- Cause and diagnosis -->
Hearing loss may be caused by a number of factors, including: [[Biology:Genetics|genetics]], ageing, exposure to noise, some [[Medicine:Infection|infection]]s, birth complications, trauma to the ear, and certain medications or toxins.<ref name=WHO2015/> A common condition that results in hearing loss is chronic ear infections.<ref name=WHO2015/> Certain infections during pregnancy, such as [[Biology:Cytomegalovirus|cytomegalovirus]], [[Medicine:Syphilis|syphilis]] and [[Medicine:Rubella|rubella]], may also cause hearing loss in the child.<ref name=WHO2015/><ref>{{cite journal | vauthors = Fowler KB | title = Congenital cytomegalovirus infection: audiologic outcome | journal = Clinical Infectious Diseases | volume = 57 Suppl 4 | issue = suppl_4 | pages = S182-4 | date = December 2013 | pmid = 24257423 | pmc = 3836573 | doi = 10.1093/cid/cit609 }}</ref> Hearing loss is diagnosed when hearing testing finds that a person is unable to hear 25 decibels in at least one ear.<ref name=WHO2015/> Testing for poor hearing is recommended for all newborns.<ref name=Las2014/> Hearing loss can be categorized as mild (25 to 40 [[Physics:Decibel|dB]]), moderate (41 to 55&nbsp;dB), moderate-severe (56 to 70&nbsp;dB), severe (71 to 90&nbsp;dB), or profound (greater than 90&nbsp;dB).<ref name=WHO2015/> There are three main types of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.<ref name=Sm2014>{{cite book | vauthors = Shearer AE, Hildebrand MS, Smith RJ | chapter = Deafness and Hereditary Hearing Loss Overview | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK1434/ | veditors =  Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJ, Stephens K, Amemiya A | title = GeneReviews [Internet] | location = Seattle (WA) | publisher = University of Washington, Seattle | date = 2014 | pmid = 20301607 }}</ref>

<!-- Prevention and treatment -->
About half of hearing loss globally is preventable through public health measures.<ref name=WHO2015/> Such practices include [[Biology:Immunization|immunization]], proper care around [[Medicine:Pregnancy|pregnancy]], avoiding loud noise, and avoiding certain medications.<ref name=WHO2015/> The [[Organization:World Health Organization|World Health Organization]] recommends that young people limit exposure to loud sounds and the use of personal audio players to an hour a day in an effort to limit exposure to noise.<ref name=WHO2015Aud>{{cite web|title=1.1 billion people at risk of hearing loss WHO highlights serious threat posed by exposure to recreational noise|url=https://www.who.int/pbd/deafness/activities/IECD_2015_Press_Release_EN.pdf?ua=1|website=who.int|access-date=2 March 2015|date=27 February 2015|url-status=live|archive-url=https://web.archive.org/web/20150501204444/http://www.who.int/pbd/deafness/activities/IECD_2015_Press_Release_EN.pdf?ua=1|archive-date=1 May 2015}}</ref> Early identification and support are particularly important in children.<ref name=WHO2015/> For many, hearing aids, [[Social:Sign language|sign language]], cochlear implants and [[Engineering:Subtitle (captioning)|subtitles]] are useful.<ref name=WHO2015/> [[Philosophy:Lip reading|Lip reading]] is another useful skill some develop.<ref name=WHO2015/> Access to hearing aids, however, is limited in many areas of the world.<ref name=WHO2015/>

<!-- Epidemiology and culture-->
As of 2013 hearing loss affects about 1.1 billion people to some degree.<ref>{{cite journal | title = Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013 | journal = Lancet | volume = 386 | issue = 9995 | pages = 743–800 | date = August 2015 | pmid = 26063472 | pmc = 4561509 | doi = 10.1016/s0140-6736(15)60692-4 | last1 = Vos | first1 = Theo | last2 = Barber | first2 = Ryan M. | last3 = Bell | first3 = Brad | last4 = Bertozzi-Villa | first4 = Amelia | last5 = Biryukov | first5 = Stan | last6 = Bolliger | first6 = Ian | last7 = Charlson | first7 = Fiona | last8 = Davis | first8 = Adrian | last9 = Degenhardt | first9 = Louisa | last10 = Dicker | first10 = Daniel | last11 = Duan | first11 = Leilei | last12 = Erskine | first12 = Holly | last13 = Feigin | first13 = Valery L. | last14 = Ferrari | first14 = Alize J. | last15 = Fitzmaurice | first15 = Christina | last16 = Fleming | first16 = Thomas | last17 = Graetz | first17 = Nicholas | last18 = Guinovart | first18 = Caterina | last19 = Haagsma | first19 = Juanita | last20 = Hansen | first20 = Gillian M. | last21 = Hanson | first21 = Sarah Wulf | last22 = Heuton | first22 = Kyle R. | last23 = Higashi | first23 = Hideki | last24 = Kassebaum | first24 = Nicholas | last25 = Kyu | first25 = Hmwe | last26 = Laurie | first26 = Evan | last27 = Liang | first27 = Xiofeng | last28 = Lofgren | first28 = Katherine | last29 = Lozano | first29 = Rafael | last30 = MacIntyre | first30 = Michael F. }}</ref> It causes disability in about 466 million people (5% of the global population), and moderate to severe disability in 124 million people.<ref name="WHO2015">{{cite web|date=March 2015|title=Deafness and hearing loss Fact sheet N°300|url=https://www.who.int/mediacentre/factsheets/fs300/en/|publisher = World Health Organization|url-status=usurped|archive-url=https://web.archive.org/web/20150516054114/http://www.who.int/mediacentre/factsheets/fs300/en/|archive-date=16 May 2015|access-date=23 May 2015}}</ref><ref name=WHO2008/><ref>{{cite journal | vauthors = Olusanya BO, Neumann KJ, Saunders JE | title = The global burden of disabling hearing impairment: a call to action | journal = Bulletin of the World Health Organization | volume = 92 | issue = 5 | pages = 367–73 | date = May 2014 | pmid = 24839326 | pmc = 4007124 | doi = 10.2471/blt.13.128728 }}</ref> Of those with moderate to severe disability 108 million live in low and middle income countries.<ref name=WHO2008>{{cite book  | title=The global burden of disease: 2004 update | year=2008 | publisher=World Health Organization | location=Geneva, Switzerland | isbn=9789241563710 | pages=35 | url=https://www.who.int/healthinfo/global_burden_disease/GBD_report_2004update_full.pdf | url-status=live | archive-url=https://web.archive.org/web/20130624134606/http://www.who.int/healthinfo/global_burden_disease/GBD_report_2004update_full.pdf | archive-date=2013-06-24 }}</ref> Of those with hearing loss, it began during childhood for 65 million.<ref name="Peads2011">{{cite book | first=Abdelaziz Y | last=Elzouki | title=Textbook of clinical pediatrics | date=2012 | publisher=Springer | location=Berlin | isbn=9783642022012 | pages=602 | url=https://books.google.com/books?id=FEf4EMjYSrgC&pg=PA602 | edition=2 | url-status=live | archive-url=https://web.archive.org/web/20151214195730/https://books.google.com/books?id=FEf4EMjYSrgC&pg=PA602 | archive-date=2015-12-14 }}</ref> Those who use sign language and are members of [[Social:Deaf culture|Deaf culture]] may see themselves as having a difference rather than a [[Social:Disability|disability]].<ref name=NAD2014>{{cite web|title=Community and Culture - Frequently Asked Questions|url=http://nad.org/issues/american-sign-language/community-and-culture-faq|website=nad.org|publisher=National Association of the Deaf|access-date=31 July 2014|url-status=live|archive-url=https://web.archive.org/web/20151227171131/http://nad.org/issues/american-sign-language/community-and-culture-faq|archive-date=27 December 2015}}</ref> Many members of Deaf culture oppose attempts to cure deafness<ref>{{cite web|title = Sound and Fury - Cochlear Implants - Essay|url = https://www.pbs.org/wnet/soundandfury/cochlear/essay.html|website = www.pbs.org|access-date = 2015-08-01|publisher = PBS|url-status = live|archive-url = https://web.archive.org/web/20150706062633/http://www.pbs.org/wnet/soundandfury/cochlear/essay.html|archive-date = 2015-07-06}}</ref><ref>{{cite web|title = Understanding Deafness: Not Everyone Wants to Be 'Fixed'|url = https://www.theatlantic.com/health/archive/2013/08/understanding-deafness-not-everyone-wants-to-be-fixed/278527/|access-date = 2015-08-01|website = www.theatlantic.com|publisher = The Atlantic|url-status = live|archive-url = https://web.archive.org/web/20150730224214/http://www.theatlantic.com/health/archive/2013/08/understanding-deafness-not-everyone-wants-to-be-fixed/278527/|archive-date = 2015-07-30|date = 2013-08-09}}</ref><ref>{{cite news|title = Why not all deaf people want to be cured|url = https://www.telegraph.co.uk/culture/9526045/Why-not-all-deaf-people-want-to-be-cured.html|access-date = 2015-08-02|website = www.telegraph.co.uk|publisher = The Daily Telegraph|url-status = live|archive-url = https://web.archive.org/web/20150924153612/http://www.telegraph.co.uk/culture/9526045/Why-not-all-deaf-people-want-to-be-cured.html|archive-date = 2015-09-24 |date = 2012-09-13|last1 = Williams|first1 = Sally }}</ref> and some within this community view cochlear implants with concern as they have the potential to eliminate their culture.<ref name=Spa2005>{{cite journal|last1=Sparrow|first1=Robert |title=Defending Deaf Culture: The Case of Cochlear Implants|journal=The Journal of Political Philosophy|date=2005|volume=13|issue=2|pages=135–152 |url=http://profiles.arts.monash.edu.au/rob-sparrow/download/Deaf-Culture.pdf|access-date=30 November 2014|doi=10.1111/j.1467-9760.2005.00217.x |s2cid=145727204 }}</ref>

==Definition==
[[File:Deaf videoconference.jpg|thumb|A deaf person using a camera-equipped smartphone to communicate in sign language]]
* Hearing loss is defined as diminished acuity to sounds which would otherwise be heard normally.<ref name="Peads2011" /> The terms hearing impaired or hard of hearing are usually reserved for people who have relative inability to hear sound in the speech frequencies. Hearing loss occurs when sound waves enter the ears and damage the sensitive tissues<ref>{{cite web |last=Mehmood |first=Amir |date=2023-01-30 |title=What causes vision loss and hearing loss? Is it because of loud music or yelling? |url=https://militaryseoblog.blogspot.com/2023/01/what-causes-vision-loss-and-hearing.html |access-date=2023-02-04 |website=militaryseoblog}}</ref> The severity of hearing loss is categorized according to the increase in intensity of sound above the usual level required for the listener to detect it.
* Deafness is defined as a degree of loss such that a person is unable to understand speech, even in the presence of amplification.<ref name="Peads2011" /> In profound deafness, even the highest intensity sounds produced by an audiometer (an instrument used to measure hearing by producing pure tone sounds through a range of frequencies) may not be detected. In total deafness, no sounds at all, regardless of amplification or method of production, can be heard.
* [[Philosophy:Speech perception|Speech perception]] is another aspect of hearing which involves the perceived clarity of a word rather than the intensity of sound made by the word. In humans, this is usually measured with speech discrimination tests, which measure not only the ability to detect sound, but also the ability to understand speech. There are very rare types of hearing loss that affect speech discrimination alone.  One example is [[Medicine:Auditory neuropathy|auditory neuropathy]], a variety of hearing loss in which the outer hair cells of the cochlea are intact and functioning, but sound information is not faithfully transmitted by the auditory nerve to the brain.<ref name="eBook1">eBook: ''Current Diagnosis & Treatment in Otolaryngology: Head & Neck Surgery'', Lalwani, Anil K. (Ed.) Chapter 44: Audiologic Testing by Brady M. Klaves, PhD, Jennifer McKee Bold, AuD, Access Medicine</ref>

Use of the terms "hearing impaired", "deaf-mute", or "deaf and dumb" to describe deaf and hard of hearing people is discouraged by many in the deaf community as well as advocacy organizations, as they are offensive to many deaf and hard of hearing people.<ref>{{cite journal |last1=Bennett |first1=ReBecca |title=Time for Change |journal=The Hearing Journal |date=May 2019 |volume=72 |issue=5 |page=16 |doi=10.1097/01.HJ.0000559500.67179.7d |doi-access=free }}</ref><ref name=NAD2016>{{cite web| title=Community and Culture - Frequently Asked Questions| url=http://nad.org/issues/american-sign-language/community-and-culture-faq| website=nad.org| publisher=National Association of the Deaf| access-date=27 January 2016| url-status=live| archive-url=https://web.archive.org/web/20151227171131/http://nad.org/issues/american-sign-language/community-and-culture-faq| archive-date=2015-12-27}}</ref>

===Hearing standards===


{{further| Physics:Equal-loudness contour| Physics:A-weighting}}

Human hearing extends in frequency from 20 to 20,000&nbsp;Hz, and in intensity from 0&nbsp;dB to 120&nbsp;dB HL or more. 0&nbsp;dB does not represent absence of sound, but rather the softest sound an average unimpaired human ear can hear; some people can hear down to −5 or even −10&nbsp;dB.  Sound is generally uncomfortably loud above 90&nbsp;dB and 115&nbsp;dB represents the threshold of pain. The ear does not hear all frequencies equally well: hearing sensitivity peaks around 3,000&nbsp;Hz.  There are many qualities of human hearing besides frequency range and intensity that cannot easily be measured quantitatively. However, for many practical purposes, normal hearing is defined by a frequency versus intensity graph, or audiogram, charting sensitivity thresholds of hearing at defined frequencies.  Because of the cumulative impact of age and exposure to noise and other acoustic insults, 'typical' hearing may not be normal.<ref>ANSI 7029:2000/BS 6951 Acoustics - Statistical distribution of hearing thresholds as a function of age</ref><ref>ANSI S3.5-1997 Speech Intelligibility Index (SII)</ref>

==Signs and symptoms==
* difficulty using the [[Engineering:Telephone|telephone]]
* loss of [[Physics:Sound localization|sound localization]]
* difficulty [[Philosophy:Speech perception|understanding speech]], especially of children and women whose voices are of a higher frequency.
* difficulty understanding speech in the presence of background noise ([[Physics:Cocktail party effect|cocktail party effect]])
* sounds or speech sounding dull, muffled or attenuated
* need for increased volume on television, radio, music and other audio sources

Hearing loss is sensory, but may have accompanying symptoms:
* pain or pressure in the ears
* a blocked feeling

There may also be accompanying secondary symptoms:
* [[Medicine:Hyperacusis|hyperacusis]], heightened sensitivity with accompanying auditory pain to certain intensities and frequencies of sound, sometimes defined as "auditory recruitment"
* [[Medicine:Tinnitus|tinnitus]], ringing, buzzing, hissing or other sounds in the ear when no external sound is present
* [[Medicine:Vertigo|vertigo]] and disequilibrium
* tympanophonia, also known as autophonia, abnormal hearing of one's own voice and respiratory sounds, usually as a result of a patulous (a constantly open) eustachian tube or dehiscent superior semicircular canals
* disturbances of facial movement (indicating a possible tumour or stroke) or in persons with [[Medicine:Bell's palsy|Bell's palsy]]

=== Complications ===
Hearing loss is associated with [[Medicine:Alzheimer's disease|Alzheimer's disease]] and [[Medicine:Dementia|dementia]].<ref>{{cite journal | vauthors = Hung SC | title = Hearing Loss is Associated With Risk of Alzheimer's Disease: A Case-Control Study in Older People | journal = Journal of Epidemiology | publisher = Journal of Epidemiol | date=Aug 2015 | volume = 25 | issue = 8 | pages = 517–521 | doi=10.2188/jea.JE20140147 | pmid = 25986155 | pmc = 4517989 }}</ref> The risk increases with the hearing loss degree. There are several hypotheses including cognitive resources being redistributed to hearing and social isolation from hearing loss having a negative effect.<ref>{{cite journal | vauthors = Thomson RS, Auduong P, Miller AT, Gurgel RK | title = Hearing loss as a risk factor for dementia: A systematic review | journal = Laryngoscope Investigative Otolaryngology | volume = 2 | issue = 2 | pages = 69–79 | date = April 2017 | pmid = 28894825 | pmc = 5527366 | doi = 10.1002/lio2.65 }}</ref> According to preliminary data, [[Engineering:Hearing aid|hearing aid]] usage can slow down the decline in cognitive functions.<ref>{{cite journal | vauthors = Hoppe U, Hesse G | title = Hearing aids: indications, technology, adaptation, and quality control | journal = GMS Current Topics in Otorhinolaryngology, Head and Neck Surgery | volume = 16 | pages = Doc08 | date = 2017-12-18 | pmid = 29279726 | pmc = 5738937 | doi = 10.3205/cto000147 }}</ref>

Hearing loss is responsible for causing thalamocortical dysrthymia in the brain which is a cause for several neurological disorders including [[Medicine:Tinnitus|tinnitus]] and [[Unsolved:Visual snow|visual snow syndrome]].

==== Cognitive decline ====
Hearing loss is an increasing concern especially in aging populations. The prevalence of hearing loss increases about two-fold for each decade increase in age after age 40.<ref>{{cite journal | vauthors = Lin FR, Niparko JK, Ferrucci L | title = Hearing loss prevalence in the United States | journal = Archives of Internal Medicine | volume = 171 | issue = 20 | pages = 1851–2 | date = November 2011 | pmid = 22083573 | doi = 10.1001/archinternmed.2011.506 | pmc = 3564588 | doi-access = free }}</ref> While the secular trend might decrease individual level risk of developing hearing loss, the prevalence of hearing loss is expected to rise due to the aging population in the US. Another concern about aging process is cognitive decline, which may progress to [[Medicine:Mild cognitive impairment|mild cognitive impairment]] and eventually dementia.<ref>{{cite journal | vauthors = Park HL, O'Connell JE, Thomson RG | title = A systematic review of cognitive decline in the general elderly population | journal = International Journal of Geriatric Psychiatry | volume = 18 | issue = 12 | pages = 1121–34 | date = December 2003 | pmid = 14677145 | doi = 10.1002/gps.1023 | s2cid = 39164724 }}</ref> The association between hearing loss and cognitive decline has been studied in various research settings. Despite the variability in study design and protocols, the majority of these studies have found consistent association between age-related hearing loss and cognitive decline, cognitive impairment, and dementia.<ref name=":0">{{cite journal | vauthors = Loughrey DG, Kelly ME, Kelley GA, Brennan S, Lawlor BA | title = Association of Age-Related Hearing Loss With Cognitive Function, Cognitive Impairment, and Dementia: A Systematic Review and Meta-analysis | journal = JAMA Otolaryngology–Head & Neck Surgery | volume = 144 | issue = 2 | pages = 115–126 | date = February 2018 | pmid = 29222544 | doi = 10.1001/jamaoto.2017.2513 | pmc = 5824986 }}</ref> The association between age-related hearing loss and Alzheimer's disease was found to be nonsignificant, and this finding supports the hypothesis that hearing loss is associated with dementia independent of Alzheimer pathology.<ref name=":0" /> There are several hypotheses about the underlying causal mechanism for age-related hearing loss and cognitive decline. One hypothesis is that this association can be explained by common etiology or shared neurobiological pathology with decline in other physiological system.<ref name=":12">{{cite journal | vauthors = Thomson RS, Auduong P, Miller AT, Gurgel RK | title = Hearing loss as a risk factor for dementia: A systematic review | journal = Laryngoscope Investigative Otolaryngology | volume = 2 | issue = 2 | pages = 69–79 | date = April 2017 | pmid = 28894825 | doi = 10.1002/lio2.65 | pmc = 5527366 | doi-access = free }}</ref> Another possible cognitive mechanism emphasize on individual's [[Philosophy:Cognitive load|cognitive load]]. As people developing hearing loss in the process of aging, the cognitive load demanded by auditory perception increases, which may lead to change in brain structure and eventually to dementia.<ref>{{cite journal | vauthors = Pichora-Fuller MK, Mick P, Reed M | title = Hearing, Cognition, and Healthy Aging: Social and Public Health Implications of the Links between Age-Related Declines in Hearing and Cognition | journal = Seminars in Hearing | volume = 36 | issue = 3 | pages = 122–39 | date = August 2015 | pmid = 27516713 | doi = 10.1055/s-0035-1555116 | pmc = 4906310 | doi-access = free }}</ref> One other hypothesis suggests that the association between hearing loss and cognitive decline is mediated through various psychosocial factors, such as decrease in [[Social:Social relation|social contact]] and increase in [[Social:Social isolation|social isolation]].<ref name=":12" /> Findings on the association between hearing loss and dementia have significant public health implication, since about 9% of dementia cases are associated with hearing loss.<ref>{{cite journal | vauthors = Ford AH, Hankey GJ, Yeap BB, Golledge J, Flicker L, Almeida OP | title = Hearing loss and the risk of dementia in later life | language = en | journal = Maturitas | volume = 112 | pages = 1–11 | date = June 2018 | pmid = 29704910 | doi = 10.1016/j.maturitas.2018.03.004 | s2cid = 13998812 | url = https://www.maturitas.org/article/S0378-5122(18)30118-X/abstract }}</ref>

==== Falls ====
[[Medicine:Falls in older adults|Falls]] have important health implications, especially for an aging population where they can lead to significant morbidity and mortality. Elderly people are particularly vulnerable to the consequences of injuries caused by falls, since older individuals typically have greater bone fragility and poorer protective reflexes.<ref name=":22">{{cite journal | vauthors = Dhital A, Pey T, Stanford MR | title = Visual loss and falls: a review | journal = Eye | volume = 24 | issue = 9 | pages = 1437–46 | date = September 2010 | pmid = 20448666 | doi = 10.1038/eye.2010.60 | doi-access = free }}</ref> Fall-related injury can also lead to burdens on the financial and health care systems.<ref name=":22" /> In literature, age-related hearing loss is found to be significantly associated with incident falls.<ref>{{cite journal | vauthors = Jiam NT, Li C, Agrawal Y | title = Hearing loss and falls: A systematic review and meta-analysis | journal = The Laryngoscope | volume = 126 | issue = 11 | pages = 2587–2596 | date = November 2016 | pmid = 27010669 | doi = 10.1002/lary.25927 | s2cid = 28871762 }}</ref> There is also a potential [[Chemistry:Dose–response relationship|dose-response relationship]] between hearing loss and falls—greater severity of hearing loss is associated with increased difficulties in postural control and increased prevalence of falls.<ref name=":32">{{cite journal | vauthors = Agmon M, Lavie L, Doumas M | title = The Association between Hearing Loss, Postural Control, and Mobility in Older Adults: A Systematic Review | journal = Journal of the American Academy of Audiology | volume = 28 | issue = 6 | pages = 575–588 | date = June 2017 | pmid = 28590900 | doi = 10.3766/jaaa.16044 | s2cid = 3744742 }}</ref> The underlying causal link between the association of hearing loss and falls is yet to be elucidated. There are several hypotheses that indicate that there may be a common process between decline in [[Biology:Auditory system|auditory system]] and increase in incident falls, driven by physiological, cognitive, and behavioral factors.<ref name=":32" /> This evidence suggests that treating hearing loss has potential to increase [[Medicine:Quality of life (healthcare)|health-related quality of life]] in older adults.<ref name=":32" />

==== Depression ====
Depression is one of the leading causes of morbidity and mortality worldwide. In older adults, the suicide rate is higher than it is for younger adults, and more suicide cases are attributable to depression.<ref>{{cite journal | vauthors = Fiske A, Wetherell JL, Gatz M | title = Depression in older adults | journal = Annual Review of Clinical Psychology | volume = 5 | issue = 1 | pages = 363–89 | date = April 2009 | pmid = 19327033 | pmc = 2852580 | doi = 10.1146/annurev.clinpsy.032408.153621 }}</ref> Different studies have been done to investigate potential risk factors that can give rise to depression in later life. Some chronic diseases are found to be significantly associated with risk of developing depression, such as coronary heart disease, [[Medicine:Respiratory disease|pulmonary disease]], [[Medicine:Visual impairment|vision loss]] and hearing loss.<ref>{{cite journal | vauthors = Huang CQ, Dong BR, Lu ZC, Yue JR, Liu QX | title = Chronic diseases and risk for depression in old age: a meta-analysis of published literature | journal = Ageing Research Reviews | volume = 9 | issue = 2 | pages = 131–41 | date = April 2010 | pmid = 19524072 | doi = 10.1016/j.arr.2009.05.005 | series = Microbes and Ageing | s2cid = 13637437 }}</ref> Hearing loss can attribute to decrease in health-related quality of life, increase in social isolation and decline in social engagement, which are all risk factors for increased risk of developing depression symptoms.<ref>{{cite journal | vauthors = Arlinger S | title = Negative consequences of uncorrected hearing loss--a review | journal = International Journal of Audiology | volume = 42 Suppl 2 | issue = sup2 | pages = 2S17–20 | date = July 2003 | pmid = 12918624 | doi = 10.3109/14992020309074639 | s2cid = 14433959 }}</ref>

==== Spoken language ability ====
[[Medicine:Post-lingual deafness|Post-lingual deafness]] is hearing loss that is sustained after the [[Social:Language acquisition|acquisition of language]], which can occur due to [[Disease|disease]], trauma, or as a side-effect of a medicine. Typically, hearing loss is gradual and often detected by family and friends of affected individuals long before the patients themselves will acknowledge the disability.<ref>{{cite journal|vauthors=Meyer C, Scarinci N, Ryan B, Hickson L|date=December 2015|title="This Is a Partnership Between All of Us": Audiologists' Perceptions of Family Member Involvement in Hearing Rehabilitation|journal=American Journal of Audiology|volume=24|issue=4|pages=536–48|doi=10.1044/2015_AJA-15-0026|pmid=26649683|s2cid=13091175}}</ref> Post-lingual deafness is far more common than pre-lingual deafness. Those who lose their hearing later in life, such as in late adolescence or adulthood, face their own challenges, living with the adaptations that allow them to live independently.

Prelingual deafness is profound hearing loss that is sustained before the acquisition of language, which can occur due to a congenital condition or through hearing loss before birth or in early infancy. Prelingual deafness impairs an individual's ability to acquire a ''spoken'' language in children, but deaf children can acquire spoken language through support from cochlear implants (sometimes combined with hearing aids).<ref>{{cite journal|vauthors=Niparko JK, Tobey EA, Thal DJ, Eisenberg LS, Wang NY, Quittner AL, Fink NE|date=April 2010|title=Spoken language development in children following cochlear implantation|journal=JAMA|volume=303|issue=15|pages=1498–506|doi=10.1001/jama.2010.451|pmc=3073449|pmid=20407059}}</ref><ref>{{cite journal|vauthors=Kral A, O'Donoghue GM|date=October 2010|title=Profound deafness in childhood|journal=The New England Journal of Medicine|volume=363|issue=15|pages=1438–50|doi=10.1056/NEJMra0911225|pmid=20925546|s2cid=13639137}}</ref> Non-signing (hearing) parents of deaf babies (90–95% of cases) usually go with oral approach without the support of sign language, as these families lack previous experience with [[Social:Sign language|sign language]] and cannot competently provide it to their children without learning it themselves. This may in some cases (late implantation or not sufficient benefit from cochlear implants) bring the risk of language deprivation for the deaf baby<ref>{{cite journal|vauthors=Hall WC|date=May 2017|title=What You Don't Know Can Hurt You: The Risk of Language Deprivation by Impairing Sign Language Development in Deaf Children|journal=Maternal and Child Health Journal|volume=21|issue=5|pages=961–965|doi=10.1007/s10995-017-2287-y|pmc=5392137|pmid=28185206}}</ref> because the deaf baby would not have a sign language if the child is unable to acquire spoken language successfully. The 5–10% of cases of deaf babies born into signing families have the potential of age-appropriate development of language due to early exposure to a ''sign language'' by sign-competent parents, thus they have the potential to meet language milestones, in sign language in lieu of spoken language.<ref>{{cite journal|last=Mayberry|first=Rachel|date=2007|title=When timing is everything: Age of first-language acquisition effects on second-language learning|journal=Applied Psycholinguistics|volume=28|issue=3|pages=537–549|doi=10.1017/s0142716407070294|doi-access=free}}</ref>

==Causes==
{{Main|Medicine:Causes of hearing loss}}
Hearing loss has multiple causes, including ageing, genetics, perinatal problems and acquired causes like noise and disease.  For some kinds of hearing loss the cause may be classified as of unknown cause.

There is a progressive loss of ability to hear high frequencies with aging known as [[Medicine:Presbycusis|presbycusis]]. For men, this can start as early as 25 and women at 30. Although genetically variable, it is a normal concomitant of ageing and is distinct from hearing losses caused by noise exposure, toxins or disease agents.<ref>{{cite journal | vauthors = Robinson DW, Sutton GJ | title = Age effect in hearing - a comparative analysis of published threshold data | journal = Audiology | volume = 18 | issue = 4 | pages = 320–34 | year = 1979 | pmid = 475664 | doi = 10.3109/00206097909072634 }}</ref> Common conditions that can increase the risk of hearing loss in elderly people are high blood pressure, [[Medicine:Diabetes|diabetes]], or the use of certain medications harmful to the ear.<ref>{{cite book | vauthors = Worrall L, Hickson LM | date = 2003 | chapter = Communication activity limitations | pages = 141–142 | veditors = Worrall LE, Hickson LM | title = Communication disability in aging: from prevention to intervention | location = Clifton Park, NY | publisher = Delmar Learning }}</ref><ref>{{cite journal | vauthors = Akinpelu OV, Mujica-Mota M, Daniel SJ | title = Is type 2 diabetes mellitus associated with alterations in hearing? A systematic review and meta-analysis | journal = The Laryngoscope | volume = 124 | issue = 3 | pages = 767–76 | date = March 2014 | pmid = 23945844 | doi = 10.1002/lary.24354 | s2cid = 25569962 }}</ref> While everyone loses hearing with age, the amount and type of hearing loss is variable.<ref>{{cite web|title=Hearing Loss and Older Adults|url=https://www.nidcd.nih.gov/health/hearing-loss-older-adults|publisher=National Institute on Deafness and Other Communication Disorders|access-date=September 11, 2016|format=Last Updated June 3, 2016|url-status=live|archive-url=https://web.archive.org/web/20161004200407/https://www.nidcd.nih.gov/health/hearing-loss-older-adults|archive-date=October 4, 2016|date=2016-01-26}}</ref>

Noise-induced hearing loss (NIHL), also known as acoustic trauma, typically manifests as elevated hearing thresholds (i.e. less sensitivity or muting). Noise exposure is the cause of approximately half of all cases of hearing loss, causing some degree of problems in 5% of the population globally.<ref name=Oishi2011>{{cite journal | vauthors = Oishi N, Schacht J | title = Emerging treatments for noise-induced hearing loss | journal = Expert Opinion on Emerging Drugs | volume = 16 | issue = 2 | pages = 235–45 | date = June 2011 | pmid = 21247358 | pmc = 3102156 | doi = 10.1517/14728214.2011.552427 }}</ref> The majority of hearing loss is not due to age, but due to noise exposure.<ref>{{cite web| url=http://blogs.cdc.gov/niosh-science-blog/2015/03/25/hl-impact-story/| title=CDC - NIOSH Science Blog – A Story of Impact....| work=cdc.gov| date=25 March 2015| url-status=live| archive-url=https://web.archive.org/web/20150613044654/http://blogs.cdc.gov/niosh-science-blog/2015/03/25/hl-impact-story/| archive-date=2015-06-13}}</ref> Various governmental, industry and standards organizations set noise standards.<ref>In the United States, United States Environmental Protection Agency, [[Organization:Occupational Safety and Health Administration|Occupational Safety and Health Administration]], [[Organization:National Institute for Occupational Safety and Health|National Institute for Occupational Safety and Health]], [[Organization:Mine Safety and Health Administration|Mine Safety and Health Administration]], and numerous state government agencies among others, set noise standards.</ref> Many people are unaware of the presence of environmental sound at damaging levels, or of the level at which sound becomes harmful. Common sources of damaging noise levels include car stereos, children's toys, motor vehicles, crowds, lawn and maintenance equipment, power tools, gun use, musical instruments, and even hair dryers. Noise damage is cumulative; all sources of damage must be considered to assess risk. In the US, 12.5% of children aged 6–19 years have permanent hearing damage from excessive noise exposure.<ref name="kid">{{cite web| url=https://www.cdc.gov/healthyyouth/noise/| title=Noise-Induced Hearing Loss: Promoting Hearing Health Among Youth| work=CDC Healthy Youth!| publisher=CDC| date=2009-07-01| url-status=live| archive-url=https://web.archive.org/web/20091221020243/http://www.cdc.gov/healthyyouth/noise/| archive-date=2009-12-21}}</ref>  The World Health Organization estimates that half of those between 12 and 35 are at risk from using personal audio devices that are too loud.<ref name="WHO2015Aud" /> Hearing loss in adolescents may be caused by loud noise from toys, music by headphones, and concerts or events.<ref>{{cite journal | vauthors = de Laat JA, van Deelen L, Wiefferink K | title = Hearing Screening and Prevention of Hearing Loss in Adolescents | journal = The Journal of Adolescent Health | volume = 59 | issue = 3 | pages = 243–245 | date = September 2016 | pmid = 27562364 | doi = 10.1016/j.jadohealth.2016.06.017 | doi-access = free }}</ref><ref>[https://www.cdc.gov/vitalsigns/hearingloss/index.html Too Loud! For Too Long! Loud noises damage hearing] ''U.S. Department of Health and Human Services, Centers for Disease Control and Prevention'', National Center for Environmental Health. (6 January 2020).</ref>

Hearing loss can be inherited. Around 75–80% of all these cases are inherited by recessive genes, 20–25% are inherited by dominant genes, 1–2% are inherited by X-linked patterns, and fewer than 1% are inherited by mitochondrial inheritance.<ref name="Harvard">{{cite web| last=Rehm| first=Heidi | title=The Genetics of Deafness; A Guide for Patients and Families| url=http://hearing.harvard.edu/info/GeneticDeafnessBookletV2.pdf| work=Harvard Medical School Center For Hereditary Deafness| publisher=Harvard Medical School| url-status=dead| archive-url=https://web.archive.org/web/20131019153702/http://hearing.harvard.edu/info/GeneticDeafnessBookletV2.pdf| archive-date=2013-10-19}}</ref>  Syndromic deafness occurs when there are other signs or medical problems aside from deafness in an individual,<ref name="Harvard" /> such as [[Medicine:Usher syndrome|Usher syndrome]], [[Medicine:Stickler syndrome|Stickler syndrome]], [[Medicine:Waardenburg syndrome|Waardenburg syndrome]], Alport's syndrome, and neurofibromatosis type 2. [[Medicine:Nonsyndromic deafness|Nonsyndromic deafness]] occurs when there are no other signs or medical problems associated with the deafness in an individual.<ref name="Harvard" />

[[Medicine:Fetal alcohol spectrum disorder|Fetal alcohol spectrum disorder]]s are reported to cause hearing loss in up to 64% of infants born to [[Medicine:Alcoholism|alcoholic]] mothers, from the ototoxic effect on the developing fetus plus malnutrition during pregnancy from the excess [[Chemistry:Ethanol|alcohol]] intake. Premature birth can be associated with sensorineural hearing loss because of an increased risk of [[Medicine:Hypoxia (medical)|hypoxia]], hyperbilirubinaemia, ototoxic medication and infection as well as noise exposure in the neonatal units. Also, hearing loss in premature babies is often discovered far later than a similar hearing loss would be in a full-term baby because normally babies are given a hearing test within 48 hours of birth, but doctors must wait until the premature baby is medically stable before testing hearing, which can be months after birth.<ref>{{cite web |title=Hearing Loss in Premature Babies |url=https://www.salusuhealth.com/Pennsylvania-Ear-Institute/Events/News-Stories/Hearing-Loss-in-Premature-Babies.aspx |website=Salus Health |publisher=Pennsylvania Ear Institute |access-date=16 August 2020 |date=2016}}</ref> The risk of hearing loss is greatest for those weighing less than 1500&nbsp;g at birth.

Disorders responsible for hearing loss include [[Medicine:Auditory neuropathy|auditory neuropathy]],<ref>{{cite journal | vauthors = Starr A, Sininger YS, Pratt H | title = The varieties of auditory neuropathy | journal = Journal of Basic and Clinical Physiology and Pharmacology | volume = 11 | issue = 3 | pages = 215–30 | date = 2011 | pmid = 11041385 | doi = 10.1515/JBCPP.2000.11.3.215 | s2cid = 31806057 }}</ref><ref>{{cite journal | vauthors = Starr A, Picton TW, Sininger Y, Hood LJ, Berlin CI | title = Auditory neuropathy | journal = Brain | volume = 119 ( Pt 3) | issue = 3 | pages = 741–53 | date = June 1996 | pmid = 8673487 | doi = 10.1093/brain/119.3.741 | doi-access = free }}</ref> [[Medicine:Down syndrome|Down syndrome]],<ref name="Rod2012">{{cite journal | vauthors = Rodman R, Pine HS | title = The otolaryngologist's approach to the patient with Down syndrome | journal = Otolaryngologic Clinics of North America | volume = 45 | issue = 3 | pages = 599–629, vii–viii | date = June 2012 | pmid = 22588039 | doi = 10.1016/j.otc.2012.03.010 }}</ref> [[Medicine:Charcot–Marie–Tooth disease|Charcot–Marie–Tooth disease]] variant 1E,<ref>{{cite web|last1=McKusick|first1=Victor A.|last2=Kniffen|first2=Cassandra L. |title=# 118300 CHARCOT-MARIE-TOOTH DISEASE AND DEAFNESS|url=http://omim.org/entry/118300|website=Online Mendelian Inheritance in Man|access-date=2 March 2018|date=30 January 2012}}</ref> [[Medicine:Autoimmune disease|autoimmune disease]], multiple sclerosis, [[Medicine:Meningitis|meningitis]], cholesteatoma, otosclerosis, perilymph fistula, [[Medicine:Ménière's disease|Ménière's disease]], recurring ear infections, strokes, superior semicircular canal dehiscence, Pierre Robin, [[Medicine:Treacher Collins syndrome|Treacher-Collins]], Usher Syndrome, [[Medicine:Pendred syndrome|Pendred Syndrome]], and [[Medicine:Turner syndrome|Turner]] syndrome, [[Medicine:Syphilis|syphilis]], [[Medicine:Vestibular schwannoma|vestibular schwannoma]], and [[Biology:Virus|viral infections]] such as [[Medicine:Measles|measles]], [[Medicine:Mumps|mumps]], congenital [[Medicine:Rubella|rubella]] (also called German measles) syndrome, several varieties of [[Biology:Herpesviridae|herpes virus]]es,<ref>{{cite journal | vauthors = Byl FM, Adour KK | title = Auditory symptoms associated with herpes zoster or idiopathic facial paralysis | journal = The Laryngoscope | volume = 87 | issue = 3 | pages = 372–9 | date = March 1977 | pmid = 557156 | doi = 10.1288/00005537-197703000-00010 | s2cid = 41226847 | doi-access = free }}</ref><ref name="Eggermont2017">{{cite book|author=Jos J. Eggermont|title=Hearing Loss: Causes, Prevention, and Treatment|url=https://books.google.com/books?id=fJExDQAAQBAJ&pg=PA198|date=22 February 2017|publisher=Elsevier Science|isbn=978-0-12-809349-8|pages=198–}}</ref> HIV/AIDS,<ref>{{cite journal | vauthors = Araújo E, Zucki F, Corteletti LC, Lopes AC, Feniman MR, Alvarenga K | title = Hearing loss and acquired immune deficiency syndrome: systematic review | journal = Jornal da Sociedade Brasileira de Fonoaudiologia | volume = 24 | issue = 2 | pages = 188–92 | date = 2012 | pmid = 22832689 | doi = 10.1590/s2179-64912012000200017 | doi-access = free }}</ref> and [[Medicine:West Nile fever|West Nile virus]].

Some medications may reversibly affect hearing. These medications are considered ototoxic. This includes loop diuretics such as furosemide and bumetanide, non-steroidal anti-inflammatory drugs (NSAIDs) both over-the-counter (aspirin, ibuprofen, naproxen) as well as prescription (celecoxib, diclofenac, etc.), paracetamol, [[Chemistry:Quinine|quinine]], and macrolide antibiotics.<ref name="Analgesic">{{cite journal | vauthors = Curhan SG, Shargorodsky J, Eavey R, Curhan GC | title = Analgesic use and the risk of hearing loss in women | journal = American Journal of Epidemiology | volume = 176 | issue = 6 | pages = 544–54 | date = September 2012 | pmid = 22933387 | pmc = 3530351 | doi = 10.1093/aje/kws146 }}</ref> Others may cause permanent hearing loss.<ref name="asha">{{cite web| url=http://www.asha.org/public/hearing/Ototoxic-Medications/| title=Ototoxic Medications (Medication Effects)| first1=Barbara| last1=Cone| first2=Patricia| last2=Dorn| first3=Dawn| last3=Konrad-Martin| first4=Jennifer| last4=Lister| first5=Candice| last5=Ortiz| first6=Kim| last6=Schairer | publisher=American Speech-Language-Hearing Association}}</ref> The most important group is the [[Chemistry:Aminoglycoside|aminoglycoside]]s (main member [[Chemistry:Gentamicin|gentamicin]]) and platinum based chemotherapeutics such as [[Biology:Cisplatin|cisplatin]] and [[Chemistry:Carboplatin|carboplatin]].<ref>{{cite journal | vauthors = Rybak LP, Mukherjea D, Jajoo S, Ramkumar V | title = Cisplatin ototoxicity and protection: clinical and experimental studies | journal = The Tohoku Journal of Experimental Medicine | volume = 219 | issue = 3 | pages = 177–86 | date = November 2009 | pmid = 19851045 | pmc = 2927105 | doi=10.1620/tjem.219.177}}</ref><ref>{{cite journal | vauthors = Rybak LP, Ramkumar V | title = Ototoxicity | journal = Kidney International | volume = 72 | issue = 8 | pages = 931–5 | date = October 2007 | pmid = 17653135 | doi = 10.1038/sj.ki.5002434 | doi-access = free }}</ref>

In addition to medications, hearing loss can also result from specific chemicals in the environment: metals, such as [[Chemistry:Lead|lead]]; solvents, such as [[Chemistry:Toluene|toluene]] (found in crude oil, [[Chemistry:Gasoline|gasoline]]<ref name="tol-nih">{{cite web| url=http://toxtown.nlm.nih.gov/text_version/chemicals.php?id=30| title=Tox Town – Toluene – Toxic chemicals and environmental health risks where you live and work – Text Version| publisher=toxtown.nlm.nih.gov| access-date=2010-06-09| url-status=live| archive-url=https://web.archive.org/web/20100609052911/http://toxtown.nlm.nih.gov/text_version/chemicals.php?id=30| archive-date=2010-06-09}}</ref> and automobile exhaust,<ref name="tol-nih" /> for example); and [[Chemistry:Asphyxiant gas|asphyxiant]]s.<ref name="def9">{{cite news| title=Addressing the Risk for Hearing Loss from Industrial Chemicals| first=Thais C.| last=Morata| url=https://www.cdc.gov/niosh/topics/noise/pubs/presentations/AOHC.swf| publisher=CDC| access-date=2008-06-05| url-status=dead| archive-url=https://web.archive.org/web/20090122171205/http://www.cdc.gov/niosh/topics/noise/pubs/presentations/AOHC.swf| archive-date=2009-01-22}}</ref> Combined with noise, these ototoxic chemicals have an additive effect on a person's hearing loss.<ref name="def9" /> Hearing loss due to chemicals starts in the high frequency range and is irreversible. It damages the [[Medicine:Cochlea|cochlea]] with lesions and degrades central portions of the [[Biology:Auditory system|auditory system]].<ref name="def9" /> For some ototoxic chemical exposures, particularly styrene,<ref name="tm">{{cite journal| last=Johnson| first=Ann-Christin| date=2008-09-09| title=Occupational exposure to chemicals and hearing impairment – the need for a noise notation| url=http://awww.arbetsmiljoverket.se/dokument/arkiv/neg/Chemicals_and_hearing_impairment.pdf| journal=Karolinska Institutet| pages=1–48| access-date=2009-06-19| archive-date=2012-09-06| url-status=dead| archive-url=https://web.archive.org/web/20120906103148/http://awww.arbetsmiljoverket.se/dokument/arkiv/neg/Chemicals_and_hearing_impairment.pdf}}</ref> the risk of hearing loss can be higher than being exposed to [[Physics:Noise|noise]] alone. The effects is greatest when the combined exposure include [[Engineering:Impulse noise (audio)|impulse noise]].<ref>{{cite journal | vauthors = Venet T, Campo P, Thomas A, Cour C, Rieger B, Cosnier F | title = The tonotopicity of styrene-induced hearing loss depends on the associated noise spectrum | journal = Neurotoxicology and Teratology | volume = 48 | pages = 56–63 | date = March 2015 | pmid = 25689156 | doi = 10.1016/j.ntt.2015.02.003 }}</ref><ref>{{cite journal | vauthors = Fuente A, Qiu W, Zhang M, Xie H, Kardous CA, Campo P, Morata TC | title = Use of the kurtosis statistic in an evaluation of the effects of noise and solvent exposures on the hearing thresholds of workers: An exploratory study | journal = The Journal of the Acoustical Society of America | volume = 143 | issue = 3 | pages = 1704–1710 | date = March 2018 | pmid = 29604694 | doi = 10.1121/1.5028368 | pmc = 8588570 | bibcode = 2018ASAJ..143.1704F | url = https://hal.archives-ouvertes.fr/hal-01844639/file/10.1121_1.5028368.pdf | doi-access = free }}</ref> A 2018 informational bulletin by the US [[Organization:Occupational Safety and Health Administration|Occupational Safety and Health Administration]] (OSHA) and the [[Organization:National Institute for Occupational Safety and Health|National Institute for Occupational Safety and Health]] (NIOSH) introduces the issue, provides examples of ototoxic chemicals, lists the industries and occupations at risk and provides prevention information.<ref>{{cite web|title=Preventing Hearing Loss Caused by Chemical (Ototoxicity) and Noise Exposure|url=https://www.cdc.gov/niosh/docs/2018-124/pdfs/2018-124.pdf|access-date=4 April 2018}}</ref>

There can be damage either to the ear, whether the external or middle ear, to the cochlea, or to the brain centers that process the aural information conveyed by the ears.  Damage to the middle ear may include fracture and discontinuity of the ossicular chain.<ref>{{cite journal |last1=Hilal |first1=Fathi |last2=Liaw |first2=Jeffrey |last3=Cousins |first3=Joseph P. |last4=Rivera |first4=Arnaldo L. |last5=Nada |first5=Ayman |date=2023-04-01 |title=Autoincudotomy as an uncommon etiology of conductive hearing loss: Case report and review of literature |journal=Radiology Case Reports |language=en |volume=18 |issue=4 |pages=1461–1465 |doi=10.1016/j.radcr.2022.10.097 |issn=1930-0433 |pmc=9925837 |pmid=36798057}}</ref><ref>{{cite journal |last1=Park |first1=Keehyun |last2=Choung |first2=Yun-Hoon |date=2009-01-01 |title=Isolated congenital ossicular anomalies |url=https://doi.org/10.1080/00016480802587846 |journal=Acta Oto-Laryngologica |volume=129 |issue=4 |pages=419–422 |doi=10.1080/00016480802587846 |issn=0001-6489 |pmid=19116789|s2cid=205395847 }}</ref>  Damage to the inner ear (cochlea) may be caused by temporal bone fracture.  People who sustain head injury are especially vulnerable to hearing loss or tinnitus, either temporary or permanent.<ref>{{cite journal | vauthors = Oesterle EC | title = Changes in the adult vertebrate auditory sensory epithelium after trauma | journal = Hearing Research | volume = 297 | pages = 91–8 | date = March 2013 | pmid = 23178236 | pmc = 3637947 | doi = 10.1016/j.heares.2012.11.010 }}</ref><ref>{{cite journal | vauthors = Eggermont JJ | title = Acquired hearing loss and brain plasticity | journal = Hearing Research | volume = 343 | pages = 176–190 | date = January 2017 | pmid = 27233916 | doi = 10.1016/j.heares.2016.05.008 | s2cid = 3568426 }}</ref>

==Pathophysiology==
[[File:Journey of Sound to the Brain.ogg|thumb|How sounds make their way from the source to the brain|275x275px]]
Sound waves reach the outer ear and are conducted down the ear canal to the [[Medicine:Eardrum|eardrum]], causing it to vibrate. The vibrations are transferred by the 3 tiny ear bones of the [[Medicine:Middle ear|middle ear]] to the fluid in the inner ear. The fluid moves hair cells ([[Biology:Stereocilia|stereocilia]]), and their movement generates nerve impulses which are then taken to the brain by the cochlear nerve.<ref>{{cite web|title=How We Hear|url=https://www.asha.org/public/hearing/how-we-hear/|website=American Speech-Language-Hearing Association|access-date=2 March 2018}}</ref><ref>{{cite web|title=How We Hear|url=https://www.sc.edu/ehs/training/Noise/hearing.htm|archive-url=https://web.archive.org/web/20170501041002/http://www.sc.edu/ehs/training/Noise/hearing.htm|archive-date=1 May 2017|url-status=dead}}</ref>  The auditory nerve takes the impulses to the brainstem, which sends the impulses to the midbrain. Finally, the signal goes to the auditory cortex of the temporal lobe to be interpreted as sound.<ref>{{cite web|title=How Do We Hear?|url=https://www.nidcd.nih.gov/health/how-do-we-hear|publisher=NIDCD|date=January 3, 2018}}</ref>

Hearing loss is most commonly caused by long-term exposure to loud noises, from recreation or from work, that damage the hair cells, which do not grow back on their own.<ref>{{cite web|title=What Is Noise-Induced Hearing Loss?|url=https://www.noisyplanet.nidcd.nih.gov/parents/what-is-noise-induced-hearing-loss|publisher=NIH - Noisy Planet|date=December 27, 2017}}</ref><ref name=NIOSH>{{cite web|title=CDC - Noise and Hearing Loss Prevention - Preventing Hearing Loss, Risk Factors - NIOSH Workplace Safety and Health Topic|url=https://www.cdc.gov/niosh/topics/noise/preventhearingloss/riskfactors.html|publisher=NIOSH/CDC|access-date=3 March 2018|date=5 February 2018}}</ref><ref name=Sch2017 />

Older people may lose their hearing from long exposure to noise, changes in the inner ear, changes in the middle ear, or from changes along the nerves from the ear to the brain.<ref>{{cite web|title=Age-Related Hearing Loss|url=https://www.nidcd.nih.gov/health/age-related-hearing-loss|publisher=NIDCD|date=18 August 2015}}</ref>

==Diagnosis==
{{Main|Medicine:Diagnosis of hearing loss}}
[[File:HearingExam.jpg|thumb|An audiologist conducting an audiometric hearing test in a sound-proof testing booth|alt=a female medical professional is seated in front of a special sound-proof booth with a glass window, controlling diagnostic test equipment. Inside the booth a middle aged man can be seen wearing headphones and is looking straight ahead of himself, not at the audiologist, and appears to be concentrating on hearing something]]

Identification of a hearing loss is usually conducted by a general practitioner medical doctor, otolaryngologist, certified and licensed audiologist, school or industrial audiometrist, or other audiometric technician. Diagnosis of the cause of a hearing loss is carried out by a specialist physician (audiovestibular physician) or otorhinolaryngologist.

Hearing loss is generally measured by playing generated or recorded sounds, and determining whether the person can hear them. Hearing sensitivity varies according to the [[Physics:Frequency|frequency]] of sounds. To take this into account, hearing sensitivity can be measured for a range of frequencies and plotted on an audiogram. Other method for quantifying hearing loss is a [[Medicine:Hearing test|hearing test]] using a mobile application or hearing aid application, which includes a hearing test.<ref name=":2">{{cite journal | vauthors = Shojaeemend H, Ayatollahi H | title = Automated Audiometry: A Review of the Implementation and Evaluation Methods | journal = Healthcare Informatics Research | volume = 24 | issue = 4 | pages = 263–275 | date = October 2018 | pmid = 30443414 | pmc = 6230538 | doi = 10.4258/hir.2018.24.4.263 }}</ref><ref name=":3">{{cite journal | vauthors = Keidser G, Convery E | title = Self-Fitting Hearing Aids: Status Quo and Future Predictions | journal = Trends in Hearing | volume = 20 | pages = 233121651664328 | date = April 2016 | pmid = 27072929 | pmc = 4871211 | doi = 10.1177/2331216516643284 }}</ref> Hearing diagnosis using mobile application is similar to the [[Medicine:Audiometry|audiometry]] procedure.<ref name=":2" /> Audiograms, obtained using mobile applications, can be used to adjust hearing aid applications.<ref name=":3" /> Another method for quantifying hearing loss is a speech-in-noise test. which gives an indication of how well one can understand speech in a noisy environment.<ref>{{cite journal | vauthors = Jansen S, Luts H, Dejonckere P, van Wieringen A, Wouters J | title = Efficient hearing screening in noise-exposed listeners using the digit triplet test | journal = Ear and Hearing | volume = 34 | issue = 6 | pages = 773–8 | date = 2013 | pmid = 23782715 | doi = 10.1097/AUD.0b013e318297920b | s2cid = 11858630 | url = https://lirias.kuleuven.be/bitstream/123456789/398543/2/Jansen_Ear%26Hearing_2013.pdf }}</ref> Otoacoustic emissions test is an objective hearing test that may be administered to toddlers and children too young to cooperate in a conventional hearing test. Auditory brainstem response testing is an electrophysiological test used to test for hearing deficits caused by pathology within the ear, the cochlear nerve and also within the brainstem.

A case history (usually a written form, with questionnaire) can provide valuable information about the context of the hearing loss, and indicate what kind of diagnostic procedures to employ. Examinations include otoscopy, [[Medicine:Tympanometry|tympanometry]], and differential testing with the [[Medicine:Weber test|Weber]], [[Medicine:Rinne test|Rinne]], Bing and Schwabach tests. In case of infection or inflammation, blood or other body fluids may be submitted for laboratory analysis.  MRI and CT scans can be useful to identify the pathology of many causes of hearing loss.

Hearing loss is categorized by severity, type, and configuration. Furthermore, a hearing loss may exist in only one ear (unilateral) or in both ears (bilateral).  Hearing loss can be temporary or permanent, sudden or progressive. The ''severity'' of a hearing loss is ranked according to ranges of nominal thresholds in which a sound must be so it can be detected by an individual. It is measured in [[Physics:Decibel|decibel]]s of hearing loss, or dB HL. There are three main ''types'' of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.<ref name="Peads2011" /> An additional problem which is increasingly recognised is [[Medicine:Auditory processing disorder|auditory processing disorder]] which is not a hearing loss as such but a difficulty perceiving sound. The shape of an audiogram shows the relative ''configuration'' of the hearing loss, such as a Carhart notch for otosclerosis, 'noise' notch for noise-induced damage, high frequency rolloff for presbycusis, or a flat audiogram for conductive hearing loss. In conjunction with speech audiometry, it may indicate central auditory processing disorder, or the presence of a schwannoma or other tumor.

People with unilateral hearing loss or single-sided deafness (SSD) have difficulty in hearing conversation on their impaired side, localizing sound, and understanding speech in the presence of background noise.  One reason for the hearing problems these patients often experience is due to the head shadow effect.<ref name="pmid15148171">{{cite journal | vauthors = Lieu JE | title = Speech-language and educational consequences of unilateral hearing loss in children | journal = Archives of Otolaryngology–Head & Neck Surgery | volume = 130 | issue = 5 | pages = 524–30 | date = May 2004 | pmid = 15148171 | doi = 10.1001/archotol.130.5.524 | doi-access = free }}</ref>

Idiopathic sudden hearing loss is a condition where a person as an immediate decrease in the sensitivity of their sensorineural hearing that does not have a known cause.<ref name=":5" /> This type of loss is usually only on one side (unilateral) and the severity of the loss varies. A common threshold of a "loss of at least 30 dB in three connected frequencies within 72 hours" is sometimes used, however there is no universal definition or international consensus for diagnosing idiopathic sudden hearing loss.<ref name=":5" /> 

==Prevention==
It is estimated that half of cases of hearing loss are preventable.<ref>{{cite book|last1=Graham|first1= John M.|last2=Baguley|first2=David M.|title=Ballantyne's Deafness |date=2009|publisher=John Wiley & Sons|location=Chichester |isbn=978-0-470-74441-3|page=16 |edition=7th|url=https://books.google.com/books?id=Of4TG61a0cQC&pg=PA16| url-status=live|archive-url=https://web.archive.org/web/20170908010428/https://books.google.com/books?id=Of4TG61a0cQC&pg=PA16|archive-date=2017-09-08}}</ref> About 60% of hearing loss in children under the age of 15 can be avoided.<ref>{{cite web|title=Hearing Loss in Children|url=https://www.cdc.gov/ncbddd/hearingloss/index.html |date = October 29, 2021 |website = U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities |access-date=17 March 2017}}</ref><ref name="WHO2015" /> There are a number of effective preventative strategies, including: immunization against [[Medicine:Rubella|rubella]] to prevent [[Medicine:Congenital rubella syndrome|congenital rubella syndrome]], immunization against ''H. influenza'' and ''S. pneumoniae'' to reduce cases of [[Medicine:Meningitis|meningitis]], and avoiding or protecting against excessive noise exposure.<ref name="Peads2011" /> The [[Organization:World Health Organization|World Health Organization]] also recommends immunization against [[Medicine:Measles|measles]], [[Medicine:Mumps|mumps]], and [[Medicine:Meningitis|meningitis]], efforts to prevent premature birth, and avoidance of certain medication as prevention.<ref>{{cite web|title=Childhood hearing loss: act now, here's how!|url=https://www.who.int/pbd/deafness/world-hearing-day/WHD2016_Brochure_EN_2.pdf|website=WHO|access-date=2 March 2016|page=6|date=2016|quote=Over 30% of childhood hearing loss is caused by diseases such as measles, mumps, rubella, meningitis and ear infections. These can be prevented through immunization and good hygiene practices. Another 17% of childhood hearing loss results from complications at birth, including prematurity, low birth weight, birth asphyxia and neonatal jaundice. Improved maternal and child health practices would help to prevent these complications. The use of ototoxic medicines in expectant mothers and newborns, which is responsible for 4% of childhood hearing loss, could potentially be avoided.|url-status=live|archive-url=https://web.archive.org/web/20160306045353/http://www.who.int/pbd/deafness/world-hearing-day/WHD2016_Brochure_EN_2.pdf|archive-date=6 March 2016}}</ref> World Hearing Day is a yearly event to promote actions to prevent hearing damage.

Avoiding exposure to loud noise can help prevent noise-induced hearing loss.<ref>{{cite web | title = Preventing Noise-Induced Hearing Loss | publisher = |website = U.S. Department of Health and Human Services, Centers for Disease Control and Prevention | date = 8 June 2020 | url = https://www.cdc.gov/ncbddd/hearingloss/noise.html | access-date = 13 July 2020}}</ref> 18% of adults exposed to loud noise at work for five years or more report hearing loss in both ears as compared to 5.5% of adults who were not exposed to loud noise at work.<ref>{{cite web |title=Quick Statistics About Hearing |url=https://www.nidcd.nih.gov/health/statistics/quick-statistics-hearing |website=NIH |date=25 March 2021 |publisher=National Institute on Deafness and Other Communication Disorders |access-date=27 October 2022}}</ref> Different programs exist for specific populations such as school-age children, adolescents and workers.<ref>{{cite journal | vauthors = Davis A, McMahon CM, Pichora-Fuller KM, Russ S, Lin F, Olusanya BO, Chadha S, Tremblay KL | title = Aging and Hearing Health: The Life-course Approach | journal = The Gerontologist | volume = 56 Suppl 2 | issue = Suppl_2 | pages = S256-67 | date = April 2016 | pmid = 26994265 | doi = 10.1093/geront/gnw033 | pmc = 6283365 }}</ref> Education regarding noise exposure increases the use of hearing protectors.<ref>{{cite journal | vauthors = El Dib RP, Mathew JL, Martins RH | title = Interventions to promote the wearing of hearing protection | journal = The Cochrane Database of Systematic Reviews | volume = 4 | issue = 4 | pages = CD005234 | date = April 2012 | pmid = 22513929 | doi = 10.1002/14651858.CD005234.pub5 | editor1-last = El Dib | editor1-first = Regina P }} {{Retracted |doi=10.1002/14651858.cd005234.pub6}}</ref> But the HPD (without individual selection, training and [[Physics:Hearing protection fit-testing|fit testing]]) does not significantly reduce the risk of hearing loss.<ref name="AIHA-6-11">{{cite book |last1=Berger |first1=Elliott H.|last2= Voix |first2= Jérémie |editor=D.K. Meinke |editor2=E.H. Berger |editor3=R. Neitzel |editor4=D.P. Driscoll |editor5=K. Bright |title=The Noise Manual |date=2018 |publisher=American Industrial Hygiene Association |location=Falls Church, Virginia |pages=255–308 |edition=6th |url=https://online-ams.aiha.org/amsssa/ecssashop.show_product_detail?p_mode=detail&p_product_serno=2719 |access-date=10 August 2022 |language=en |chapter=Chapter 11: Hearing Protection Devices}}</ref><ref name="Groenewold-2014">{{cite journal |author=Groenewold M.R. |author2=Masterson E.A. |author3=Themann C.L. |author4=Davis R.R. |title=Do hearing protectors protect hearing? |journal=American Journal of Industrial Medicine |date=2014 |volume=57 |issue=9 |pages=1001–1010 |doi=10.1002/ajim.22323 |pmid=24700499 |url=https://stacks.cdc.gov/view/cdc/36768 |access-date=15 October 2022 |publisher=Wiley Periodicals |pmc=4671486 |issn=1097-0274}}</ref> The use of [[Biology:Antioxidant|antioxidant]]s is being studied for the prevention of noise-induced hearing loss, particularly for scenarios in which noise exposure cannot be reduced, such as during military operations.<ref>{{cite journal | vauthors = Stucken EZ, Hong RS | title = Noise-induced hearing loss: an occupational medicine perspective | journal = Current Opinion in Otolaryngology & Head and Neck Surgery | volume = 22 | issue = 5 | pages = 388–93 | date = October 2014 | pmid = 25188429 | doi = 10.1097/moo.0000000000000079 | s2cid = 22846225 }}</ref>

===Workplace noise regulation===
Noise is widely recognized as an occupational hazard. In the United States, the [[Organization:National Institute for Occupational Safety and Health|National Institute for Occupational Safety and Health]] (NIOSH) and the [[Organization:Occupational Safety and Health Administration|Occupational Safety and Health Administration]] (OSHA) work together to provide standards and enforcement on workplace noise levels.<ref>{{cite web|url=https://www.cdc.gov/niosh/topics/noise/|title=Noise and Hearing Loss Prevention |website=Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health|access-date=July 15, 2016|url-status=live|archive-url=https://web.archive.org/web/20160709222707/http://www.cdc.gov/niosh/topics/noise/|archive-date=July 9, 2016}}</ref><ref>{{cite web|url=https://www.osha.gov/SLTC/noisehearingconservation/standards.html|title=Safety and Health Topics: Occupational Noise Exposure |website=Occupational Safety and Health Administration|access-date=July 15, 2015|url-status=live|archive-url=https://web.archive.org/web/20160506050548/https://www.osha.gov/SLTC/noisehearingconservation/standards.html|archive-date=May 6, 2016}}</ref> The hierarchy of hazard controls demonstrates the different levels of controls to reduce or eliminate exposure to noise and prevent hearing loss, including [[Engineering:Engineering controls|engineering controls]] and [[Social:Personal protective equipment|personal protective equipment]] (PPE).<ref>{{cite web|url=https://www.cdc.gov/niosh/topics/noisecontrol/#The%2520Hierarchy%2520of%2520Control|title=Controls for Noise Exposure |website=Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health|access-date=July 15, 2016|url-status=live|archive-url=https://web.archive.org/web/20160704113757/http://www.cdc.gov/niosh/topics/noisecontrol/#The%2520Hierarchy%2520of%2520Control|archive-date=July 4, 2016}}</ref> Other programs and initiative have been created to prevent hearing loss in the workplace. For example, the Safe-in-Sound Award was created to recognize organizations that can demonstrate results of successful noise control and other interventions.<ref>{{cite web|url=http://www.safeinsound.us/|title=Excellence in Hearing Loss Prevention Award |website=Safe-in-Sound|access-date=July 15, 2016|url-status=live|archive-url=https://web.archive.org/web/20160527193835/http://www.safeinsound.us/|archive-date=May 27, 2016}}</ref> Additionally, the [[Engineering:Buy Quiet|Buy Quiet]] program was created to encourage employers to purchase quieter machinery and tools.<ref>{{cite web|url=https://www.cdc.gov/niosh/topics/buyquiet/default.html|title=Buy Quiet |website=Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health|access-date=July 15, 2016|url-status=live|archive-url=https://web.archive.org/web/20160808151558/http://www.cdc.gov/niosh/topics/buyquiet/default.html|archive-date=August 8, 2016}}</ref> By purchasing less noisy power tools like those found on the [[Engineering:NIOSH Power Tools Database|NIOSH Power Tools Database]] and limiting exposure to ototoxic chemicals, great strides can be made in preventing hearing loss.<ref>{{cite web|url=http://wwwn.cdc.gov/niosh-sound-vibration/|title=PowerTools Database |website=Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health|access-date=July 15, 2016|url-status=live|archive-url=https://web.archive.org/web/20160630135841/http://wwwn.cdc.gov/niosh-sound-vibration/|archive-date=June 30, 2016}}</ref>

Companies can also provide personal hearing protector devices tailored to both the worker and type of employment. Some hearing protectors universally block out all noise, and some allow for certain noises to be heard. Workers are more likely to wear hearing protector devices when they are properly fitted.<ref>{{cite journal|url=https://www.cdc.gov/niosh/docs/2010-136/|title=  Occupationally-Induced Hearing Loss | department = Publication number 2010-136|website = U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health.|url-status=live|archive-url=https://web.archive.org/web/20160512031928/http://www.cdc.gov/niosh/docs/2010-136/|archive-date=2016-05-12|doi=10.26616/NIOSHPUB2010136|year=2010|doi-access=free}}</ref>

Often interventions to prevent noise-induced hearing loss have many components. A 2017 Cochrane review found that stricter legislation might reduce noise levels.<ref name=":1">{{cite journal | vauthors = Tikka C, Verbeek JH, Kateman E, Morata TC, Dreschler WA, Ferrite S | title = Interventions to prevent occupational noise-induced hearing loss | journal = The Cochrane Database of Systematic Reviews | volume = 7 | pages = CD006396 | date = July 2017 | issue = 7 | pmid = 28685503 | pmc = 6353150 | doi = 10.1002/14651858.cd006396.pub4 }}</ref>  Providing workers with information on their sound exposure levels was not shown to decrease exposure to noise. Ear protection, if used correctly, can reduce noise to safer levels, but often, providing them is not sufficient to prevent hearing loss. Engineering noise out and other solutions such as proper maintenance of equipment can lead to noise reduction, but further field studies on resulting noise exposures following such interventions are needed. Other possible solutions include improved enforcement of existing legislation and better implementation of well-designed prevention programmes, which have not yet been proven conclusively to be effective. The conclusion of the Cochrane Review was that further research could modify what is now regarding the effectiveness of the evaluated interventions.<ref name=":1" />

The Institute for Occupational Safety and Health of the German Social Accident Insurance has created a hearing impairment calculator based on the ISO 1999 model for studying threshold shift in relatively homogeneous groups of people, such as workers with the same type of job.  The ISO 1999 model estimates how much hearing impairment in a group can be ascribed to age and [[Physics:Sound exposure|noise exposure]].  The result is calculated via an [[Algebraic equation|algebraic equation]] that uses the A-weighted sound exposure level, how many years the people were exposed to this noise, how old the people are, and their sex. The model's estimations are only useful for people without hearing loss due to non-job related exposure and can be used for prevention activities.<ref>{{cite web|last=Institute for Occupational Safety and Health of the German Social Accident Insurance|title=Hearing impairment calculator|url=https://www.dguv.de/ifa/praxishilfen/noise/gefaehrdungsbeurteilung-und-unterweisung/software-berechnung-von-hoerschwellenverschiebungen/index.jsp}}</ref>

===Screening===
The United States Preventive Services Task Force recommends neonatal hearing screening for all newborns, as the first three years of life are believed to be the most important for language development.<ref name=Las2014/><ref>{{cite web |date=2021-11-09 |title=Your Baby's Hearing Screening and Next Steps {{!}} NIDCD |url=https://www.nidcd.nih.gov/health/your-babys-hearing-screening-and-next-steps |access-date=2023-06-21 |website=www.nidcd.nih.gov |language=en}}</ref> Universal neonatal hearing screenings have now been widely implemented across the U.S., with rates of newborn screening increasing from less than 3% in the early 1990s to 98% in 2009.<ref>{{cite web |title=Recommended Uniform Screening Panel {{!}} HRSA |url=https://www.hrsa.gov/advisory-committees/heritable-disorders/rusp |access-date=2023-06-21 |website=www.hrsa.gov}}</ref><ref>{{cite journal |last1=Gaffney |first1=Marcus |last2=Eichwald |first2=John |last3=Gaffney |first3=Claudia |last4=Alam |first4=Suhana |last5=Centers for Disease Control and Prevention (CDC) |date=2014-09-12 |title=Early hearing detection and intervention among infants--hearing screening and follow-up survey, United States, 2005-2006 and 2009-2010 |url=https://pubmed.ncbi.nlm.nih.gov/25208254/ |journal=MMWR Supplements |volume=63 |issue=2 |pages=20–26 |issn=2380-8942 |pmid=25208254}}</ref> Newborns whose screening reveals a high index of suspicion of hearing loss are referred for additional diagnostic testing with the goal of providing early intervention and access to language.<ref>{{cite journal |last1=Wilson |first1=James Maxwell Glover |last2=Jungner |first2=Gunnar |last3=Organization |first3=World Health |date=1968 |title=Principles and practice of screening for disease |journal=Public Health Papers |number=34 |hdl=10665/37650 |url=https://apps.who.int/iris/handle/10665/37650 |language=en}}</ref> 

The American Academy of Pediatrics advises that children should have their hearing tested several times throughout their schooling:<ref name="kid" />
* When they enter school
* At ages 6, 8, and 10
* At least once during [[Social:Middle school|middle school]]
* At least once during high school
While the American College of Physicians indicated that there is not enough evidence to determine the utility of screening in adults over 50 years old who do not have any symptoms,<ref name="annals">{{cite journal | url=http://annals.org/article.aspx?articleid=1309706 | title=Screening for Hearing Loss in Older Adults: U.S. Preventive Services Task Force Recommendation Statement | publisher=The American College of Physicians | journal=Annals of Internal Medicine | first=Virginia A. | last=Moyer | date=2012-11-06 | volume=157 | issue=9 | pages=655–661 | doi=10.7326/0003-4819-157-9-201211060-00526 | pmid=22893115 | s2cid=29265879 | access-date=2012-11-06 | url-status=live | archive-url=https://web.archive.org/web/20121027083232/http://annals.org/article.aspx?articleid=1309706 | archive-date=2012-10-27 }}</ref> the American Language, Speech Pathology and Hearing Association recommends that adults should be screened at least every decade through age 50 and at three-year intervals thereafter, to minimize the detrimental effects of the untreated condition on quality of life.<ref>{{cite web|url=http://www.asha.org/public/hearing/Who-Should-be-Screened/|title=Who Should be Screened for Hearing Loss|website=www.asha.org|access-date=2017-03-17|archive-url=https://web.archive.org/web/20170317235022/http://www.asha.org/public/hearing/Who-Should-be-Screened/|archive-date=2017-03-17|url-status=dead}}</ref> For the same reason, the US Office of Disease Prevention and Health Promotion included as one of Healthy People 2020 objectives: to increase the proportion of persons who have had a hearing examination.<ref>{{cite web|url=https://www.healthypeople.gov/2020/topics-objectives/topic/hearing-and-other-sensory-or-communication-disorders/objectives|title=Hearing and Other Sensory or Communication Disorders {{!}} Healthy People 2020|website=www.healthypeople.gov|access-date=2017-03-17|url-status=live|archive-url=https://web.archive.org/web/20170318002053/https://www.healthypeople.gov/2020/topics-objectives/topic/hearing-and-other-sensory-or-communication-disorders/objectives|archive-date=2017-03-18}}</ref>

==Management==
[[File:Hearing aid 20080620.jpg|thumb|An in-the-canal hearing aid]]
Management depends on the specific cause if known as well as the extent, type and configuration of the hearing loss. Sudden hearing loss due to an underlying nerve problem may be treated with corticosteroids.<ref>{{cite journal | vauthors = Chandrasekhar SS, Tsai Do BS, Schwartz SR, Bontempo LJ, Faucett EA, Finestone SA, Hollingsworth DB, Kelley DM, Kmucha ST, Moonis G, Poling GL, Roberts JK, Stachler RJ, Zeitler DM, Corrigan MD, Nnacheta LC, Satterfield L, Monjur TM | title = Clinical Practice Guideline: Sudden Hearing Loss (Update) Executive Summary | journal =   Otolaryngology–Head and Neck Surgery | volume = 161 | issue = 2 | pages = 195–210 | date = August 2019 | pmid = 31369349 | doi = 10.1177/0194599819859883 | doi-access = free }}</ref>

Most hearing loss, that resulting from age and noise, is progressive and irreversible, and there are currently no approved or recommended treatments.  A few specific kinds of hearing loss are amenable to surgical treatment.  In other cases, treatment is addressed to underlying pathologies, but any hearing loss incurred may be permanent. Some management options include [[Engineering:Hearing aid|hearing aid]]s, [[Cochlear implant|cochlear implant]]s, [[Medicine:Middle ear implant|middle ear implant]]s, [[Engineering:Assistive technology|assistive technology]], and [[Engineering:Closed captioning|closed captioning]];<ref name=Sch2017 /> in movie theaters, a Hearing Impaired (HI) audio track may be available via headphones to better hear dialog.<ref name=":43">{{cite web |title=Accessibility & The Audio Track File |url=https://cinepedia.com/accessibility/accessibility-the-audio-track-file/ |access-date=14 November 2023 |website=Cinepedia}}</ref>

This choice depends on the level of hearing loss, type of hearing loss, and personal preference. Hearing aid applications are one of the options for hearing loss management.<ref name=":3" /><ref>{{cite journal |last1=Koo |first1=Miseung |last2=Nguyen |first2=Willy |last3=Lee |first3=Jun Ho |last4=Oh |first4=Seung-Ha |last5=Kyun Park |first5=Moo |date=September 2022 |title=Behavioral Evaluation of 3 Smartphone-Based Hearing Aid Apps for Patients with Mild Hearing Loss: An Exploratory Pilot Study |journal=The Journal of International Advanced Otology |volume=18 |issue=5 |pages=399–404 |doi=10.5152/iao.2022.21469 |issn=2148-3817 |pmc=9524353 |pmid=36063096}}</ref> For people with bilateral hearing loss, it is not clear if bilateral hearing aids (hearing aids in both ears) are better than a unilateral hearing aid (hearing aid in one ear).<ref name="Sch2017" />

=== Idiopathic sudden hearing loss ===
For people with idiopathic sudden hearing loss, different treatment approaches have been suggested that are usually based on the suspected cause of the sudden hearing loss. Treatment approaches may include corticosteroid medications, rheological drugs, vasodilators, anesthetics, and other medications chosen based on the suspected underlying pathology that caused the sudden hearing loss.<ref name=":5">{{cite journal |last1=Plontke |first1=Stefan K. |last2=Meisner |first2=Christoph |last3=Agrawal |first3=Sumit |last4=Cayé-Thomasen |first4=Per |last5=Galbraith |first5=Kevin |last6=Mikulec |first6=Anthony A. |last7=Parnes |first7=Lorne |last8=Premakumar |first8=Yaamini |last9=Reiber |first9=Julia |last10=Schilder |first10=Anne Gm |last11=Liebau |first11=Arne |date=2022-07-22 |title=Intratympanic corticosteroids for sudden sensorineural hearing loss |url= |journal=The Cochrane Database of Systematic Reviews |volume=2022 |issue=7 |pages=CD008080 |doi=10.1002/14651858.CD008080.pub2 |issn=1469-493X |pmc=9307133 |pmid=35867413}}</ref> The evidence supporting most treatment options for idiopathic sudden hearing loss is very weak and adverse effects of these different medications is a consideration when deciding on a treatment approach.<ref name=":5" />

==Epidemiology==
[[File:Hearing loss (adult onset) world map - DALY - WHO2004.svg|thumb|upright=1.4|[[Disability-adjusted life year]] for hearing loss (adult onset) per 100,000&nbsp;inhabitants in 2004:
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{{legend|#ff2c00|655–700}}
{{legend|#cb0000|>700}}
{{col-end}}]]

Globally, hearing loss affects about 10% of the population to some degree.<ref name=Oishi2011/> It caused moderate to severe disability in 124.2&nbsp;million people as of 2004 (107.9&nbsp;million of whom are in low and middle income countries).<ref name=WHO2008/> Of these 65&nbsp;million acquired the condition during childhood.<ref name="Peads2011"/> At birth ~3 per 1000 in developed countries and more than 6 per 1000 in developing countries have hearing problems.<ref name="Peads2011" />

Hearing loss increases with age. In those between 20 and 35 rates of hearing loss are 3% while in those 44 to 55 it is 11% and in those 65 to 85 it is 43%.<ref name=Las2014/>

A 2017 report by the World Health Organization estimated the costs of unaddressed hearing loss and the cost-effectiveness of interventions, for the health-care sector, for the education sector and as broad societal costs.<ref>{{cite book|title=Global costs of unaddressed hearing loss and cost-effectiveness of interventions: a WHO report|last=World Health Organization|first=WHO|publisher=World Health Organization|year=2017|isbn=978-92-4-151204-6|location=Geneva|pages=5–10}}</ref>  Globally, the annual cost of unaddressed hearing loss was estimated to be in the range of $750–790 billion international dollars.

The [[Organization:International Organization for Standardization|International Organization for Standardization]] (ISO) developed the ISO 1999 standards for the estimation of hearing thresholds and noise-induced hearing impairment.<ref>{{cite book|title=Acoustics—Estimation of noise induced hearing loss.|last=ISO|first=International Organization for Standardization|publisher=International Organization for Standardization|year=2013|location=Geneva, Switzerland|pages=20}}</ref> They used data from two noise and hearing study databases, one presented by Burns and Robinson (''Hearing and Noise in Industry,'' Her Majesty's Stationery Office,  London, 1970) and by Passchier-Vermeer (1968).<ref>{{cite book|title=Hearing loss due to exposure to steady state broadband noise|last=Passchier-Vermeer|first=W|publisher=TNO, Instituut voor gezondheidstechniek|year=1969|location=Delft, Netherlands|pages=Report 35 Identifier 473589}}</ref> As race are some of the factors that can affect the expected distribution of pure-tone hearing thresholds several other national or regional datasets exist, from Sweden,<ref>{{cite journal | vauthors = Johansson M, Arlinger S | title = Reference data for evaluation of occupationally noise-induced hearing loss | journal = Noise & Health | volume = 6 | issue = 24 | pages = 35–41 | date = 2004-07-07 | pmid = 15703139 }}</ref>  Norway,<ref>{{cite journal | vauthors = Tambs K, Hoffman HJ, Borchgrevink HM, Holmen J, Engdahl B | title = Hearing loss induced by occupational and impulse noise: results on threshold shifts by frequencies, age and gender from the Nord-Trøndelag Hearing Loss Study | journal = International Journal of Audiology | volume = 45 | issue = 5 | pages = 309–17 | date = May 2006 | pmid = 16717022 | doi = 10.1080/14992020600582166 | s2cid = 35123521 }}</ref> South Korea,<ref>{{cite journal | vauthors = Jun HJ, Hwang SY, Lee SH, Lee JE, Song JJ, Chae S | title = The prevalence of hearing loss in South Korea: data from a population-based study | journal = The Laryngoscope | volume = 125 | issue = 3 | pages = 690–4 | date = March 2015 | pmid = 25216153 | doi = 10.1002/lary.24913 | s2cid = 11731976 }}</ref> the United States<ref>{{cite journal | vauthors = Flamme GA, Deiters K, Needham T | title = Distributions of pure-tone hearing threshold levels among adolescents and adults in the United States by gender, ethnicity, and age: Results from the US National Health and Nutrition Examination Survey | journal = International Journal of Audiology | volume = 50 | pages = S11-20 | date = March 2011 | issue = Suppl 1 | pmid = 21288063 | doi = 10.3109/14992027.2010.540582 | s2cid = 3396617 }}</ref> and Spain.<ref>{{cite journal | vauthors = Rodríguez Valiente A, Roldán Fidalgo A, García Berrocal JR, Ramírez Camacho R | title = Hearing threshold levels for an otologically screened population in Spain | journal = International Journal of Audiology | volume = 54 | issue = 8 | pages = 499–506 | date = August 2015 | pmid = 25832123 | doi = 10.3109/14992027.2015.1009643 | s2cid = 143590528 }}</ref>

In the United States hearing is one of the health outcomes measure by the National Health and Nutrition Examination Survey (NHANES), a survey [[Research|research]] program conducted by the National Center for Health Statistics. It examines health and [[Biology:Nutrition|nutrition]]al status of adults and children in the {{wipe|United States}}.  Data from the United States in 2011-2012 found that rates of hearing loss has declined among adults aged 20 to 69 years, when compared with the results from an earlier time period (1999-2004). It also found that adult hearing loss is associated with increasing age, sex, ethnicity, educational level, and noise exposure.<ref>{{cite journal | vauthors = Hoffman HJ, Dobie RA, Losonczy KG, Themann CL, Flamme GA | title = Declining Prevalence of Hearing Loss in US Adults Aged 20 to 69 Years | journal = JAMA Otolaryngology–Head & Neck Surgery | volume = 143 | issue = 3 | pages = 274–285 | date = March 2017 | pmid = 27978564 | pmc = 5576493 | doi = 10.1001/jamaoto.2016.3527 }}</ref>  Nearly one in four adults had audiometric results suggesting noise-induced hearing loss. Almost one in four adults who reported excellent or good hearing had a similar pattern (5.5% on both sides and 18% on one side). Among people who reported exposure to loud noise at work, almost one third had such changes.<ref>{{cite journal | vauthors = Carroll YI, Eichwald J, Scinicariello F, Hoffman HJ, Deitchman S, Radke MS, Themann CL, Breysse P | title = Vital Signs: Noise-Induced Hearing Loss Among Adults - United States 2011-2012 | journal = MMWR. Morbidity and Mortality Weekly Report | volume = 66 | issue = 5 | pages = 139–144 | date = February 2017 | pmid = 28182600 | pmc = 5657963 | doi = 10.15585/mmwr.mm6605e3 }}</ref>

==Social and cultural aspects==
{{Main|Medicine:Social impact of profound hearing loss|Social:Deaf culture}}
[[File:Drawing (sign language friend), 2008.jpg|thumb|The sign for "friend" in [[Social:American Sign Language|American Sign Language]]]]
People with extreme hearing loss may communicate through [[Social:Sign language|sign language]]s. Sign languages convey meaning through manual communication and body language instead of acoustically conveyed sound patterns. This involves the simultaneous combination of hand shapes, orientation and movement of the hands, arms or body, and facial expressions to express a speaker's thoughts. "Sign languages are based on the idea that vision is the most useful tool a deaf person has to communicate and receive information".<ref>{{cite web|title=American Sign Language|url=https://www.nidcd.nih.gov/health/american-sign-language#1|website=NIDCD|access-date=17 November 2016|url-status=live|archive-url=https://web.archive.org/web/20161115163913/https://www.nidcd.nih.gov/health/american-sign-language#1|archive-date=15 November 2016|date=2015-08-18}}</ref>

[[Social:Deaf culture|Deaf culture]] refers to a tight-knit cultural group of people whose primary language is signed, and who practice social and cultural norms which are distinct from those of the surrounding hearing community. This community does not automatically include all those who are clinically or legally deaf, nor does it exclude every hearing person. According to Baker and Padden, it includes any person or persons who "identifies him/herself as a member of the Deaf community, and other members accept that person as a part of the community,"<ref name="book22">{{cite book|last=Baker|first=Charlotte|title=American Sign Language: A Look at Its Story, Structure and Community|author2=Carol Padden|year=1978}}</ref> an example being [[Medicine:Child of deaf adult|children of deaf adults]] with normal hearing ability.  It includes the set of social beliefs, behaviors, art, literary traditions, history, values, and shared institutions of communities that are influenced by deafness and which use sign languages as the main means of communication.<ref name="padden20053">{{cite book|last1=Padden|first1=Carol A.|url=https://books.google.com/books?id=2B4XWIFPgowC&q=Deaf&pg=PA1|title=Inside Deaf Culture|last2=Humphries|first2=Tom (Tom L.)|publisher=Harvard University Press|year=2005|isbn=978-0-674-01506-7|location=Cambridge, MA|page=1}}</ref><ref name="bigD3">{{cite web|author=Jamie Berke|date=9 February 2010|title=Deaf Culture - Big D Small D|url=http://deafness.about.com/cs/culturefeatures1/a/bigdorsmalld.htm|access-date=22 November 2013|publisher=About.com|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304111043/http://deafness.about.com/cs/culturefeatures1/a/bigdorsmalld.htm|url-status=dead}}</ref>  Members of the Deaf community tend to view deafness as a difference in human experience rather than a [[Social:Disability|disability]] or [[Disease|disease]].<ref name="ladd20032">{{cite book|last=Ladd|first=Paddy|url=https://books.google.com/books?id=7PRLjkES83oC|title=Understanding Deaf Culture: In Search of Deafhood|publisher=Multilingual Matters|year=2003|isbn=978-1-85359-545-5|page=502|author-link=Paddy Ladd}}</ref><ref name="lane20112">{{cite book|last=Lane|first=Harlan L.|url=https://books.google.com/books?id=KySGdskgT9EC&pg=PA1|title=The People of the Eye: Deaf Ethnicity and Ancestry|author2=Richard Pillard|author3=Ulf Hedberg|publisher=Oxford University Press|year=2011|isbn=978-0-19-975929-3|page=269}}</ref>  When used as a cultural label especially within the culture, the word ''deaf'' is often written with a capital ''D'' and referred to as "big&nbsp;D Deaf" in speech and sign. When used as a label for the [[Physics:Audiology|audiological]] condition, it is written with a lower case ''d''.<ref name="padden20053" /><ref name="bigD3" />

There also multiple educational institutions for both deaf and Deaf people, that usually use sign language as the main language of instruction. Famous institutions include Gallaudet University and the [[Organization:National Technical Institute for the Deaf|National Technical Institute for the Deaf]] in the US,<ref>{{cite web|title=Top Deaf universities and colleges|url=https://www.healthyhearing.com/report/52682-Top-universities-for-deaf-students|access-date=2021-08-12|website=Healthy Hearing|language=en-US}}</ref> and the National University Corporation of Tsukuba University of Technology in Japan.<ref>{{cite web|title=Tsukuba University of Technology Home|url=https://www.tsukuba-tech.ac.jp/english/index.html|access-date=2021-08-12|website=www.tsukuba-tech.ac.jp}}</ref>

== Research ==

===Stem cell transplant and gene therapy===
A 2005 study achieved successful regrowth of cochlea cells in guinea pigs.<ref>{{cite web | url=https://www.newscientist.com/article.ns?id=dn7003 | title=Gene therapy is first deafness 'cure' | work=NewScientist.com News Service | first=Andy | last=Coghlan | date=2005-02-14 | url-status=live | archive-url=https://web.archive.org/web/20080914114532/http://www.newscientist.com/article.ns?id=dn7003 | archive-date=2008-09-14 }}</ref> However, the regrowth of cochlear hair cells does not imply the restoration of hearing sensitivity, as the sensory cells may or may not make connections with neurons that carry the signals from hair cells to the brain. A 2008 study has shown that gene therapy targeting [[Biology:ATOH1|Atoh1]] can cause hair cell growth and attract neuronal processes in embryonic mice. Some hope that a similar treatment will one day ameliorate hearing loss in humans.<ref>{{cite journal | vauthors = Gubbels SP, Woessner DW, Mitchell JC, Ricci AJ, Brigande JV | title = Functional auditory hair cells produced in the mammalian cochlea by in utero gene transfer | journal = Nature | volume = 455 | issue = 7212 | pages = 537–41 | date = September 2008 | pmid = 18754012 | pmc = 2925035 | doi = 10.1038/nature07265 | bibcode = 2008Natur.455..537G }}</ref>

Recent research, reported in 2012 achieved growth of cochlear nerve cells resulting in hearing improvements in gerbils,<ref name="Nature">{{cite journal | url=http://www.nature.com/news/human-embryonic-stem-cells-restore-gerbil-hearing-1.11402 | title=Human embryonic stem cells restore gerbil hearing | journal=Nature News | first=Virginia | last=Gewin | url-status=live | date=2012-09-12 | access-date=2013-01-22 | doi=10.1038/nature.2012.11402 | s2cid=87417776 | archive-url=https://web.archive.org/web/20121214055556/http://www.nature.com/news/human-embryonic-stem-cells-restore-gerbil-hearing-1.11402 | archive-date=2012-12-14 }}</ref> using stem cells. Also reported in 2013 was regrowth of hair cells in deaf adult mice using a drug intervention resulting in hearing improvement.<ref>{{cite web | url=http://life.nationalpost.com/2013/01/10/drug-may-reverse-permanent-deafness-by-regenerating-cells-of-inner-ear-harvard-study/ | title=Drug may reverse permanent deafness by regenerating cells of inner ear: Harvard study | work=National Post | first=Davida | last=Ander | url-status=dead | archive-url=https://archive.today/20130216121920/http://life.nationalpost.com/2013/01/10/drug-may-reverse-permanent-deafness-by-regenerating-cells-of-inner-ear-harvard-study/ | archive-date=2013-02-16 }}</ref> The Hearing Health Foundation in the US has embarked on a project called the Hearing Restoration Project.<ref name="HHF">{{cite web | url=http://www.hearinghealthfoundation.org/ | title=Hearing Health Foundation | publisher=HHF | url-status=live | access-date=2013-01-22 | archive-url=https://web.archive.org/web/20130127111102/http://hearinghealthfoundation.org/ | archive-date=2013-01-27 }}</ref> Also Action on Hearing Loss in the UK is also aiming to restore hearing.<ref name="Action">{{cite web | url=http://www.actiononhearingloss.org.uk/your-hearing/biomedical-research.aspx | title=Biomedical research – Action On Hearing Loss | publisher=RNID | access-date=2013-01-22 | archive-url=https://web.archive.org/web/20130123105056/http://www.actiononhearingloss.org.uk/your-hearing/biomedical-research.aspx | archive-date=2013-01-23 | url-status=dead }}</ref>

Researchers reported in 2015 that genetically deaf mice which were treated with [[Biology:TMC1|TMC1]] gene therapy recovered some of their hearing.<ref>{{cite news|last= Gallacher|first= James|date= 9 July 2015|title= Deafness could be treated by virus, say scientists|url= https://www.bbc.co.uk/news/health-33442820|publisher= BBC|location= UK|access-date= 9 July 2015|url-status= live|archive-url= https://web.archive.org/web/20150709112049/http://www.bbc.co.uk/news/health-33442820|archive-date= 9 July 2015}}</ref><ref>{{cite journal|vauthors=Askew C, Rochat C, Pan B, Asai Y, Ahmed H, Child E, Schneider BL, Aebischer P, Holt JR|date=July 2015|title=Tmc gene therapy restores auditory function in deaf mice|journal=Science Translational Medicine|volume=7|issue=295|pages=295ra108|doi=10.1126/scitranslmed.aab1996|pmid=26157030|pmc=7298700}}<!--|access-date=8 July 2015--></ref> In 2017, additional studies were performed to treat [[Medicine:Usher syndrome|Usher syndrome]]<ref name="pmid28254438">{{cite journal | vauthors = Isgrig K, Shteamer JW, Belyantseva IA, Drummond MC, Fitzgerald TS, Vijayakumar S, Jones SM, Griffith AJ, Friedman TB, Cunningham LL, Chien WW | title = Gene Therapy Restores Balance and Auditory Functions in a Mouse Model of Usher Syndrome | journal = Molecular Therapy | volume = 25 | issue = 3 | pages = 780–791 | date = March 2017 | pmid = 28254438 | pmc = 5363211 | doi = 10.1016/j.ymthe.2017.01.007 }}</ref> and here, a recombinant adeno-associated virus seemed to outperform the older vectors.<ref name="pmid28165475">{{cite journal | vauthors = Landegger LD, Pan B, Askew C, Wassmer SJ, Gluck SD, Galvin A, Taylor R, Forge A, Stankovic KM, Holt JR, Vandenberghe LH | title = A synthetic AAV vector enables safe and efficient gene transfer to the mammalian inner ear | journal = Nature Biotechnology | volume = 35 | issue = 3 | pages = 280–284 | date = March 2017 | pmid = 28165475 | pmc = 5340646 | doi = 10.1038/nbt.3781 }}</ref><ref name="pmid28165476">{{cite journal | vauthors = Pan B, Askew C, Galvin A, Heman-Ackah S, Asai Y, Indzhykulian AA, Jodelka FM, Hastings ML, Lentz JJ, Vandenberghe LH, Holt JR, Géléoc GS | title = Gene therapy restores auditory and vestibular function in a mouse model of Usher syndrome type 1c | journal = Nature Biotechnology | volume = 35 | issue = 3 | pages = 264–272 | date = March 2017 | pmid = 28165476 | pmc = 5340578 | doi = 10.1038/nbt.3801 }}</ref>

===Audition===
Besides research studies seeking to improve hearing, such as the ones listed above, research studies on the deaf have also been carried out in order to understand more about audition. Pijil and Shwarz (2005) conducted their study on the deaf who lost their hearing later in life and, hence, used cochlear implants to hear. They discovered further evidence for rate coding of pitch, a system that codes for information for frequencies by the rate that neurons fire in the auditory system, especially for lower frequencies as they are coded by the frequencies that neurons fire from the basilar membrane in a synchronous manner. Their results showed that the subjects could identify different pitches that were proportional to the frequency stimulated by a single electrode. The lower frequencies were detected when the basilar membrane was stimulated, providing even further evidence for rate coding.<ref name="Carlson, N. R. 2010">{{cite book | vauthors = Carlson NR | date = 2010 | title = Physiology of behavior | edition = 11th | location = Upper Saddle River, New Jersey | publisher = Pearson Education, Inc }}</ref>

== See also ==
* [[Physics:Audiology|Audiology]]
* [[Medicine:Deaf hearing|Deaf hearing]]
* H.870
* [[Physics:Safe listening|Safe listening]]
* World Hearing Day

==References==
{{Reflist}}

==External links==
{{Medical condition classification and resources
| ICD10          = {{ICD10|H|90||h|90}}–{{ICD10|H|91||h|90}}
| ICD9           = {{ICD9|389}}
| MedlinePlus     = 003044
| eMedicineSubj   = article
| eMedicineTopic  = 994159
| eMedicine_mult  =
| MeshID         = D034381
| DiseasesDB=19942
}}

* [https://www.who.int/news-room/fact-sheets/detail/deafness-and-hearing-loss WHO fact sheet on deafness and hearing loss]
* {{curlie|Kids_and_Teens/Health/Conditions_and_Diseases/Deafness/}}
* [https://www.nidcd.nih.gov/health/hearing-ear-infections-deafness National Institute for the Prevention of Deafness and other Communication Disorders]
* [https://apps.who.int/iris/bitstream/handle/10665/254659/9789241512046-eng.pdf?sequence=1 Global Costs of unaddressed hearing loss and cost-effectiveness of interventions] [[Organization:World Health Organization Composite International Diagnostic Interview|World Health Organization]]. 2017. [https://web.archive.org/web/20200512085900/https://apps.who.int/iris/bitstream/handle/10665/254659/9789241512046-eng.pdf?sequence=1 Internet archive] on 12 May 2020.
* [https://www.cdc.gov/niosh/topics/noise/default.html Occupational Noise and Hearing Loss Prevention] ''U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health.'' (6 February 2018).
* Global Audiology, International Society of Audiology
* International Ototoxicity Management Group

{{Diseases of the ear and mastoid process}}

[[Category:Communication disorders]]
[[Category:Wikipedia medicine articles ready to translate]]
[[Category:Deafness]]

{{Sourceattribution|Hearing loss}}