|
==Causes==
{{Main| Causes Noise-inducedof 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 [[idiopathic|of unknown cause]].
===Age===
There is a progressive loss of ability to hear high frequencies with aging known as [[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, 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 }}</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) 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> ▼
===Noise===
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| 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]], [[Occupational Safety and Health Administration]], [[National Institute for Occupational Safety and Health]], [[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>
▲{{Main| Noise-induced hearing loss}}
{{globalize| section| date=December 2015}}
▲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 [[National Institute for Occupational Safety and Health]] (NIOSH) recognizes that the majority of hearing loss is not due to age, but due to noise exposure. By correcting for age in assessing hearing, one tends to overestimate the hearing loss due to noise for some and underestimate it for others.<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| 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>
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 | name-list-format = vanc | 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 [[Usher syndrome]], [[Stickler syndrome]], [[Waardenburg syndrome]], [[Alport's syndrome]], and [[neurofibromatosis type 2]]. [[Nonsyndromic deafness]] occurs when there are no other signs or medical problems associated with an individual other than deafness.<ref name="Harvard" /> ▼Hearing loss due to noise may be temporary, called a 'temporary threshold shift', a reduced sensitivity to sound over a wide frequency range resulting from exposure to a brief but very loud noise like a gunshot, firecracker, jet engine, jackhammer, etc. or to exposure to loud sound over a few hours such as during a pop concert or nightclub session.<ref>{{Cite web|url=https://www.osha.gov/dts/osta/otm/noise/health_effects/effects.html|title=Noise and Hearing Conservation: Effects of Excessive Exposure |website=Occupational Safety & Health Administration|access-date=July 14, 2016|url-status=dead|archive-url=https://web.archive.org/web/20160629163619/https://www.osha.gov/dts/osta/otm/noise/health_effects/effects.html|archive-date=June 29, 2016}}</ref> Recovery of hearing is usually within 24 hours, but may take up to a week.<ref>{{Cite web|url=https://www.sfu.ca/sonic-studio/handbook/Threshold_Shift.html|title=Threshold Shift (TS)|website=Simon Fraser University|access-date=2016-07-14|url-status=dead|archive-url=https://web.archive.org/web/20160503122331/http://www.sfu.ca/sonic-studio/handbook/Threshold_Shift.html|archive-date=2016-05-03}}</ref> Both constant exposure to loud sounds (85 dB(A) or above) and one-time exposure to extremely loud sounds (120 dB(A) or above) may cause permanent hearing loss.<ref>{{Cite web|url=https://www.cdc.gov/healthyschools/noise/signs.htm|title=About Hearing Loss |website=Centers for Disease Control and Prevention|access-date=2016-07-15|url-status=dead|archive-url=https://web.archive.org/web/20160720230923/http://www.cdc.gov/healthyschools/noise/signs.htm|archive-date=2016-07-20}}</ref>
*[[Fetal alcohol spectrum disorder]]s are reported to cause hearing loss in up to 64% of infants born to [[alcoholism|alcoholic]] mothers, from the ototoxic effect on the developing fetus plus malnutrition during pregnancy from the excess [[ethanol|alcohol]] intake. [[Premature birth]] can be associated with sensorineural hearing loss because of an increased risk of [[hypoxia (medical)|hypoxia]], [[hyperbilirubinaemia]], ototoxic medication and infection as well as noise exposure in the neonatal units. The risk of hearing loss is greatest for those weighing less than 1500 g at birth. ▼[[Noise-induced hearing loss]] (NIHL) typically manifests as elevated hearing thresholds (i.e. less sensitivity or muting) between 3000 and 6000 Hz, centred at 4000 Hz. As noise damage progresses, damage spreads to affect lower and higher frequencies. On an [[audiogram]], the resulting configuration has a distinctive notch, called a 'noise' notch. As ageing and other effects contribute to higher frequency loss (6–8 kHz on an audiogram), this notch may be obscured and entirely disappear.
Disorders responsible for hearing loss include [[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 | url = https://semanticscholar.org/paper/d77e3cdcf9e3576a1cf6a685bdff3c3cc45cafab }}</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> [[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> [[Charcot–Marie–Tooth disease]] variant 1E,<ref>{{cite web|last1=McKusick|first1=Victor A.|last2=Kniffen|first2=Cassandra L. | name-list-format = vanc |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> [[autoimmune disease]], [[multiple sclerosis]], [[meningitis]], [[cholesteatoma]], [[otosclerosis]], [[perilymph fistula]], [[Ménière's disease]], recurring ear infections, strokes, [[superior semicircular canal dehiscence]], [[Pierre Robin syndrome|Pierre Robin]], [[Treacher Collins syndrome|Treacher-Collins]], [[Retinitis pigmentosa|Retinitis Pigmentosa]], [[Pendred syndrome|Pedreds]], and [[Turner syndrome|Turners]] syndrome, [[syphilis]], [[vestibular schwannoma]], and [[Virus|viral infections]] such as [[measles]], [[mumps]], congenital [[rubella]] (also called German measles) syndrome, several varieties of [[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 }}</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 [[West Nile fever|West Nile virus]].
Various governmental, industry and standards organizations set noise standards.<ref>In the United States, [[United States Environmental Protection Agency]], [[Occupational Safety and Health Administration]], [[National Institute for Occupational Safety and Health]], [[Mine Safety and Health Administration]], and numerous state government agencies among others, set noise standards.</ref>
Some medications may reversibly affect hearing. These medications are considered [[Ototoxicity|ototoxic]]. This includes [[loop diuretic]]s such as furosemide and bumetanide, [[non-steroidal anti-inflammatory drug]]s (NSAIDs) both over-the-counter (aspirin, ibuprofen, naproxen) as well as prescription (celecoxib, diclofenac, etc.), paracetamol, [[quinine]], and [[macrolide antibiotics]] . The link between NSAIDs and hearing loss tends to be greater in women, especially those who take ibuprofen six or more times a week.<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 | name-list-format = vanc | publisher=American Speech-Language-Hearing Association| access-date= }}</ref> The most important group is the [[aminoglycoside]]s (main member [[gentamicin]]) and platinum based chemotherapeutics such as [[cisplatin]] and [[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 }}</ref> ▼The [[U.S. Environmental Protection Agency]] has identified the level of 70 dB(A) (40% louder to twice as loud as normal conversation; typical level of TV, radio, stereo; city street noise) for 24‑hour exposure as the level necessary to protect the public from hearing loss and other disruptive effects from noise, such as sleep disturbance, stress-related problems, learning detriment, etc.<ref>Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety. Document ID: usepa-1974</ref> Noise levels are typically in the 65 to 75 dB (A) range for those living near airports or freeways and may result in hearing damage if sufficient time is spent outdoors.<ref>{{Cite web|url=http://www.sanda.org.za/index.php/resources-links/deafness|title=Deafness | website=SANDRA: South African National Deaf Association|access-date=2016-07-14|url-status=dead|archive-url=https://web.archive.org/web/20160801152215/http://www.sanda.org.za/index.php/resources-links/deafness|archive-date=2016-08-01}}</ref>
In addition to medications, hearing loss can also result from specific chemicals in the environment: metals, such as [[lead]]; [[solvents]], such as [[toluene]] (found in [[crude oil]], [[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 [[asphyxiant gas|asphyxiant]]s.<ref name="def9">{{cite news| title=Addressing the Risk for Hearing Loss from Industrial Chemicals| first=Thais C.| last=Morata| name-list-format = vanc | 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 [[cochlea]] with lesions and degrades central portions of the [[auditory system]].<ref name="def9" /> For some ototoxic chemical exposures, particularly styrene,<ref name="tm">{{cite journal| last=Johnson| first=Ann-Christin| name-list-format = vanc | 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 [[noise]] alone. The effects is greatest when the combined exposure include [[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 | bibcode = 2018ASAJ..143.1704F | url = https://hal.archives-ouvertes.fr/hal-01844639/file/10.1121_1.5028368.pdf }}</ref> A 2018 informational bulletin by the US [[Occupational Safety and Health Administration]] (OSHA) and the [[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> ▼
Louder sounds cause damage in a shorter period of time. Estimation of a "safe" duration of exposure is possible using an ''exchange rate'' of 3 dB. As 3 dB represents a doubling of the intensity of sound, duration of exposure must be cut in half to maintain the same energy dose. For workplace noise regulation, the "safe" daily exposure amount at 85 dB A, known as an [[exposure action value]], is 8 hours, while the "safe" exposure at 91 dB(A) is only 2 hours.<ref>Occupational Noise Exposure, National Institute for Occupational Safety and Health 98-126</ref>
Different standards use exposure action values between 80dBA and 90dBA. Note that for some people, sound may be damaging at even lower levels than 85 dB A. Exposures to other ototoxins (such as pesticides, some medications including chemotherapy agents, solvents, etc.) can lead to greater susceptibility to noise damage, as well as causing its own damage. This is called a ''synergistic'' interaction. Since noise damage is cumulative over long periods of time, persons who are exposed to non-workplace noise, like recreational activities or environmental noise, may have compounding damage from all sources.
Some national and international organizations and agencies use an exchange rate of 4 dB or 5 dB.<ref>{{cite web| url=http://www.msha.gov/regs/complian/guides/noise/g3appendixb.htm| title=Compliance Guide to MSHA's Occupational Noise Exposure Standard, APPENDIX B – GLOSSARY OF TERMS| url-status=dead| archive-url=https://web.archive.org/web/20131112204458/http://www.msha.gov/regs/complian/guides/noise/g3appendixb.htm| archive-date=2013-11-12| access-date=2013-11-12}}</ref> While these exchange rates may indicate a wider zone of comfort or safety, they can significantly underestimate the damage caused by loud noise. For example, at 100 dB (nightclub music level), a 3 dB exchange rate would limit exposure to 15 minutes; the 5 dB exchange rate allows an hour.
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. If one is exposed to loud sound (including music) at high levels or for extended durations (85 dB A or greater), then hearing loss will occur. Sound intensity (sound energy, or propensity to cause damage to the ears) increases dramatically with proximity according to an inverse square law: halving the distance to the sound quadruples the sound intensity.
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 due to noise has been described as primarily a condition of modern society.<ref name=Go2007>{{cite journal| last1=Goines| first1=Lisa| last2=Hagler| first2=Louis| name-list-format = vanc | title=Noise Pollution: A Modern Plague| journal=Southern Medical Journal| date=March 2007| volume=100| issue=3| pages=287–294 | citeseerx=10.1.1.504.8717| doi=10.1097/smj.0b013e3180318be5| pmid=17396733}}</ref> In preindustrial times, humans had far less exposure to loud sounds. Studies of primitive peoples indicate that much of what has been attributed to age-related hearing loss may be long term cumulative damage from all sources, especially noise. People living in preindustrial societies have considerably less hearing loss than similar populations living in modern society. Among primitive people who have migrated into modern society, hearing loss is proportional to the number of years spent in modern society.<ref>{{cite journal | vauthors = Rosen S, Bergman M, Plester D, El-Mofty A, Satti MH | title = Presbycusis study of a relatively noise-free population in the Sudan | journal = The Annals of Otology, Rhinology, and Laryngology | volume = 71 | issue = 3 | pages = 727–43 | date = September 1962 | pmid = 13974856 | doi = 10.1177/000348946207100313 }}</ref><ref>{{cite journal | vauthors = Bergman M | title = Hearing in the Mabaans. A critical review of related literature | journal = Archives of Otolaryngology | volume = 84 | issue = 4 | pages = 411–5 | date = October 1966 | pmid = 5921716 | doi = 10.1001/archotol.1966.00760030413007 }}</ref><ref>{{cite journal | vauthors = Goycoolea MV, Goycoolea HG, Farfan CR, Rodriguez LG, Martinez GC, Vidal R | title = Effect of life in industrialized societies on hearing in natives of Easter Island | journal = The Laryngoscope | volume = 96 | issue = 12 | pages = 1391–6 | date = December 1986 | pmid = 3784745 | doi = 10.1288/00005537-198612000-00015 }}</ref> Military service in [[World War II]], the [[Korean War]], and the [[Vietnam War]], has likely also caused hearing loss in large numbers of men from those generations, though proving that hearing loss was a direct result of military service is problematic without entry and exit audiograms.<ref>{{cite book| author=Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Medical Follow-up Agency| editor1-last=Humes| editor1-first=Larry| editor2-last=Joellenbeck| editor2-first=Lois| editor3-last=Durch| editor3-first=Jane| name-list-format = vanc | title=Noise and military service : implications for hearing loss and tinnitus| date=2006| publisher=THE NATIONAL ACADEMIES PRESS| ___location=500 Fifth Street, N.W., Washington, DC 20001| isbn=978-0-309-09949-3| pages=72–111| url=http://www.silere.com/Noise%20and%20Military%20Service.pdf| access-date=26 November 2014| format=eBook| url-status=dead| archive-url=https://web.archive.org/web/20141224144530/http://www.silere.com/Noise%20and%20Military%20Service.pdf| archive-date=24 December 2014}}</ref>
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> In 2017, the [[Centers for Disease Control and Prevention]] brought their researchers together with experts from the [[World Health Organization]] and academia to examine the risk of hearing loss from excessive noise exposure in and outside the workplace in different age groups, as well as actions being taken to reduce the burden of the condition. A summary report was published in 2018.<ref>{{cite journal | vauthors = Murphy WJ, Eichwald J, Meinke DK, Chadha S, Iskander J | title = CDC Grand Rounds: Promoting Hearing Health Across the Lifespan | journal = MMWR. Morbidity and Mortality Weekly Report | volume = 67 | issue = 8 | pages = 243–246 | date = March 2018 | pmid = 29494567 | pmc = 5861697 | doi = 10.15585/mmwr.mm6708a2 }}</ref>
===Genetic===
▲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 | name-list-format = vanc | 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>
When looking at the genetics of deafness, there are 2 different forms, syndromic and [[Nonsyndromic deafness|nonsyndromic]]. Syndromic deafness occurs when there are other signs or medical problems aside from deafness in an individual. This accounts for around 30% of deaf individuals who are deaf from a genetic standpoint.<ref name=Harvard /> Nonsyndromic deafness occurs when there are no other signs or medical problems associated with an individual other than deafness. From a genetic standpoint, this accounts for the other 70% of cases, and represents the majority of hereditary hearing loss.<ref name=Harvard /> Syndromic cases occur with disorders such as [[Usher syndrome]], [[Stickler syndrome]], [[Waardenburg syndrome]], [[Alport's syndrome]], and [[neurofibromatosis type 2]]. These are diseases that have deafness as one of the symptoms or as a common feature associated with it. Many of the genetic mutations giving rise to syndromic deafness have been identified. In nonsyndromic cases, where deafness is the only finding, it is more difficult to identify the genetic mutation although some have been discovered.
* Gene mapping has identified the genetic locations for several nonsyndromic dominant (DFNA#) and recessive (DFNB#) forms of deafness. The first gene mapped for non-syndromic deafness, DFNA1, involves a splice site mutation in the formin related homolog diaphanous 1 (DIAPH1). A single base change in a large [[Costa Rica]]n family was identified as causative in a rare form of low frequency onset progressive hearing loss with autosomal dominant inheritance exhibiting variable age of onset and complete penetrance by age 30.<ref>{{cite journal | vauthors = Lynch ED, Lee MK, Morrow JE, Welcsh PL, León PE, King MC | title = Nonsyndromic deafness DFNA1 associated with mutation of a human homolog of the Drosophila gene diaphanous | journal = Science | volume = 278 | issue = 5341 | pages = 1315–8 | date = November 1997 | pmid = 9360932 | doi = 10.1126/science.278.5341.1315 | bibcode = 1997Sci...278.1315L | url = https://semanticscholar.org/paper/d51fd6fc618b2769b79b82df451e5aace6f1f993 }}</ref> The most common type of congenital hearing loss in developed countries is DFNB1, also known as connexin 26 deafness or [[GJB2]]-related deafness.
* The most common dominant syndromic forms of hearing loss include [[Stickler syndrome]] and [[Waardenburg syndrome]].
* The most common recessive syndromic forms of hearing loss are [[Pendred syndrome]] and [[Usher syndrome]].
* The congenital defect [[microtia]], deformed or unformed outer ear, can be associated with partial or complete conductive deafness, depending upon the severity of the deformity and whether the middle ear is also affected. It can also be associated with abnormalities of the inner ear giving rise to an additional sensorineural component to the hearing loss (mixed deafness).
*Dozens of additional genes for nonsyndromic deafness have been identified.<ref>hereditaryhearingloss.org/</ref>
===Perinatal problems===
* [[Fetal alcohol spectrum disorder]]s are reported to cause hearing loss in up to 64% of infants born to [[alcoholism|alcoholic]] mothers, from the ototoxic effect on the developing fetus plus malnutrition during pregnancy from the excess [[ethanol|alcohol]] intake.
▲* [[Premature birth]] can be associated with sensorineural hearing loss because of an increased risk of [[hypoxia (medical)|hypoxia]], [[hyperbilirubinaemia]], ototoxic medication and infection as well as noise exposure in the neonatal units. The risk of hearing loss is greatest for those weighing less than 1500 g at birth.
===Disorders===
*[[Auditory neuropathy]] a disorder of poor speech perception even though the tympanic membrane, middle ear structures, and cochlear nerve are intact.<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 | url = https://semanticscholar.org/paper/d77e3cdcf9e3576a1cf6a685bdff3c3cc45cafab }}</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> People with auditory neuropathy may have normal hearing or hearing loss ranging from mild to severe.
*Inherited disorders
** People with [[Down syndrome]] are more likely to have hearing loss.<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> This is usually due to middle ear effusions in childhood but towards the end of the second decade they may develop a high frequency sensorineural hearing loss which may progressively worsen.
**[[Charcot–Marie–Tooth disease]] variant 1E (CMT1E) is noted for demyelinating in addition to deafness.<ref>{{cite web|last1=McKusick|first1=Victor A.|last2=Kniffen|first2=Cassandra L. | name-list-format = vanc |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>
**[[Autoimmune disease]] is recognized as a cause for cochlear damage. Although rare, it is possible for autoimmune processes to target the cochlea specifically as a first presentation. [[Granulomatosis with polyangiitis]] is one of the autoimmune conditions that may precipitate hearing loss. [[Cogan's syndrome]] commonly presents with hearing loss.
**[[Multiple sclerosis]] can have an effect on hearing as well. Multiple sclerosis, or MS, is an [[autoimmune disease]] where the immune system attacks the [[myelin sheath]], a covering that protects the nerves. If the auditory nerve becomes damaged, the affected person will become completely deaf in one or both ears. There is no cure for MS.
*[[Meningitis]] may damage the auditory nerve or the cochlea.
*[[Cholesteatoma]] is a (acquired or congenital) benign collection of squamous epithelial cells within the middle ear. Acquired cholesteatomas are commonly caused by repeated middle ear infections
*[[Otosclerosis]] is a condition that can cause fixation of the stapes (or stirrup) in the middle ear preventing its movement and causing a conductive hearing loss.
*[[Perilymph fistula]] – a microtear in either the round or oval window (membranes separating the middle and inner ear) of the cochlea causing perilymph to leak into the middle ear. This usually occurs as a consequence of trauma, including barotrauma, and can give rise to vertigo as well as hearing loss.
*[[Ménière's disease]] (endolymphatic hydrops) occurs when there is an elevated pressure in the endolymph in the cochlea. Its symptoms include fluctuating low frequency hearing loss, aural fullness, [[tinnitus]], and dizziness lasting for hours
*Recurring ear infections or concomitant secondary infections (such as bacterial infection subsequent to viral infection) can result in hearing loss
*Strokes – Depending on what blood vessels are affected by the stroke, one of the symptoms can be deafness
*[[Superior semicircular canal dehiscence]], a gap in the bone cover above the inner ear, can lead to low-frequency conductive hearing loss, autophony and vertigo.
*Syndromic hearing loss can be either [[Conductive hearing loss|conductive]] or [[Sensorineural hearing loss|sensorineural]]. It occurs with abnormalities in other parts of the bodies. Examples include [[Pierre Robin syndrome|Pierre Robin]], [[Treacher Collins syndrome|Treacher-Collins]], [[Retinitis pigmentosa|Retinitis Pigmentosa]], [[Pendred syndrome|Pedreds]], and [[Turner syndrome|Turners]] syndrome, among others.
* [[Syphilis]] is commonly transmitted from pregnant women to their fetuses, and about a third of infected children will eventually become deaf.
*[[Vestibular schwannoma]], erroneously known as [[Acoustic neuroma]]s, and other types of [[brain tumor]]s can cause hearing loss by infringement of the tumor on the [[vestibulocochlear nerve]]
*[[Virus|Viral infections]] of the ear can cause sensorineural hearing loss usually as the consequence of a labyrinthitis. The person may be generally unwell at the time.
**[[Measles]] may cause [[Vestibulocochlear nerve|auditory nerve]] damage but usually gives rise to a chronic middle ear problem giving rise to a mixed hearing loss.
**[[Mumps]] (Epidemic parotitis) may result in profound sensorineural hearing loss (90 dB or more), unilateral (one ear) or bilateral (both ears).
** congenital [[rubella]] (also called German measles) syndrome, can cause deafness in newborns
** several varieties of [[Herpesviridae|herpes virus]]es that cause other diseases can also infect the ear, and can result in hearing loss: congenital infection with [[cytomegalovirus]] is responsible for deafness in newborn children and also progressive sensorineural hearing loss in childhood; [[herpes simplex]] type 1, oral herpes associated with cold sores; [[Epstein Barr]] virus that causes mononucleosis; [[varicella zoster]] oticus that causes facial paralysis ([[Ramsay Hunt syndrome]])<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 }}</ref>
** People with [[HIV/AIDS]] may develop hearing problems due to medications they take for the disease, the [[HIV virus]], or due to an increased rate of other infections.<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>
**[[West Nile fever|West Nile virus]], which can cause a variety of neurological disorders, can also cause hearing loss by attacking the auditory nerve.
===Medications===
▲Some medications may reversibly affect hearing. These medications are considered [[Ototoxicity|ototoxic]]. This includes [[loop diuretic]]s such as furosemide and bumetanide, [[non-steroidal anti-inflammatory drug]]s (NSAIDs) both over-the-counter (aspirin, ibuprofen, naproxen) as well as prescription (celecoxib, diclofenac, etc.), paracetamol, [[quinine]], and [[macrolide antibiotics]]. The link between NSAIDs and hearing loss tends to be greater in women, especially those who take ibuprofen six or more times a week.<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 | name-list-format = vanc | publisher=American Speech-Language-Hearing Association| access-date= }}</ref> The most important group is the [[aminoglycoside]]s (main member [[gentamicin]]) and platinum based chemotherapeutics such as [[cisplatin]] and [[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 }}</ref>
In 2007, the [[Food and Drug Administration (United States)|U.S. Food and Drug Administration]] (FDA) warned about possible sudden hearing loss from [[PDE5 inhibitor]]s, which are used for erectile dysfunction.<ref name="FDA-PDE5">{{cite web| url=https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/2007/ucm109012.htm| title=FDA Announces Revisions to Labels for Cialis, Levitra and Viagra| date=2007-10-18| publisher=[[Food and Drug Administration]]| access-date=2011-10-30| url-status=live| archive-url=https://web.archive.org/web/20111023051639/https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/2007/ucm109012.htm| archive-date=2011-10-23}}</ref>
Audiologic monitoring for ototoxicity allows for the (1) early detection of changes to hearing status presumably attributed to a drug/treatment regime so that changes in the drug regimen may be considered, and (2) audiologic intervention when handicapping hearing impairment has occurred.<ref>{{cite web |title=Ototoxicity Monitoring |url=https://audiology.org/publications-resources/document-library/ototoxicity-monitoring |website=Audiology |accessdate=10 August 2019 |language=en |date=12 June 2014}}</ref>
Co-administration of anti-oxidants and ototoxic medications may limit the extent of the ototoxic damage<ref>{{cite journal | vauthors = Yorgason JG, Fayad JN, Kalinec F | title = Understanding drug ototoxicity: molecular insights for prevention and clinical management | journal = Expert Opinion on Drug Safety | volume = 5 | issue = 3 | pages = 383–99 | date = May 2006 | pmid = 16610968 | doi = 10.1517/14740338.5.3.383 }}</ref><ref>{{cite journal | vauthors = Kranzer K, Elamin WF, Cox H, Seddon JA, Ford N, Drobniewski F | title = A systematic review and meta-analysis of the efficacy and safety of N-acetylcysteine in preventing aminoglycoside-induced ototoxicity: implications for the treatment of multidrug-resistant TB | journal = Thorax | volume = 70 | issue = 11 | pages = 1070–7 | date = November 2015 | pmid = 26347391 | doi = 10.1136/thoraxjnl-2015-207245 | doi-access = free }}</ref>
===Chemicals===
{{Main| Ototoxicity}}
In addition to medications, hearing loss can also result from specific chemicals in the environment: metals, such as [[lead]]; [[solvents]], such as [[toluene]] (found in [[crude oil]], [[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 [[asphyxiant gas|asphyxiant]]s.<ref name="def9">{{cite news| title=Addressing the Risk for Hearing Loss from Industrial Chemicals| first=Thais C.| last=Morata| name-list-format = vanc | 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 [[cochlea]] with lesions and degrades central portions of the [[auditory system]].<ref name="def9" /> For some ototoxic chemical exposures, particularly styrene,<ref name="tm">{{cite journal| last=Johnson| first=Ann-Christin| name-list-format = vanc | 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 [[noise]] alone. The effects is greatest when the combined exposure include [[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 | bibcode = 2018ASAJ..143.1704F | url = https://hal.archives-ouvertes.fr/hal-01844639/file/10.1121_1.5028368.pdf }}</ref>
*[[Solvent]]s
**[[toluene]], [[styrene]], [[xylene]], [[Hexane|''n''-hexane]], [[ethyl benzene]], [[white spirit| white spirits/Stoddard]], [[carbon disulfide]], [[jet fuel]], [[perchloroethylene]], [[trichloroethylene]], [[P-Xylene|''p''-xylene]]<ref>{{cite journal | vauthors = Sliwinska-Kowalska M, Zamyslowska-Szmytke E, Szymczak W, Kotylo P, Fiszer M, Wesolowski W, Pawlaczyk-Luszczynska M | title = Exacerbation of noise-induced hearing loss by co-exposure to workplace chemicals | journal = Environmental Toxicology and Pharmacology | volume = 19 | issue = 3 | pages = 547–53 | date = May 2005 | pmid = 21783525 | doi = 10.1016/j.etap.2004.12.018 }}</ref>
*Asphyxiants
**[[carbon monoxide]], [[hydrogen cyanide]]
*[[Heavy metal (chemistry)|Heavy metal]]s
**lead, [[mercury (element)|mercury]], [[cadmium]], [[arsenic]], [[organotin compound|tin-hydrocarbon compound]]s (trimethyltin)
*[[Pesticide]]s and [[herbicide]]s – The evidence is weak regarding association between herbicides and hearing loss; hearing loss in such circumstances may be due to concommitant exposure to insecticides.
**[[paraquat]], [[organophosphate]]s
A 2018 informational bulletin by the US [[Occupational Safety and Health Administration]] (OSHA) and the [[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>
===Physical trauma===
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. Damage to the inner ear (cochlea) may be caused by [[Bony labyrinth|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 }}</ref>
|
