HOME

TheInfoList




Hearing loss is a partial or total inability to
hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through an organ such as the ear. The academic field concerned wit ...

hear
. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to
acquire ''Acquire'' is a multi-player mergers and acquisitions themed board game Board games are tabletop games that typically use moved or placed on a pre-marked board (playing surface) and often include elements of table, Card game, card, Role-pl ...
spoken
language A language is a structured system of communication Communication (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the ...

language
, and in adults it can create difficulties with social interaction and at work. Hearing loss can be temporary or permanent. Hearing loss related to age usually affects both ears and is due to
cochlear hair cell Hair cells are the sensory receptors of both the auditory system The auditory system is the sensory system for the sense of hearing. It includes both the ear, sensory organs (the ears) and the auditory parts of the sensory system. System ove ...
loss. In some people, particularly older people, hearing loss can result in loneliness.
Deaf people Deaf people are typically defined as those who have profound hearing impairment in both ears as a result of either acquired or congenital hearing loss. Such people may be associated with deaf culture. Deafness (little to no hearing) is distinguished ...
usually have little to no hearing. Hearing loss may be caused by a number of factors, including:
genetics Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, ...

genetics
,
ageing Ageing or aging (see spelling differences Despite the various English dialects Dialect The term dialect (from Latin , , from the Ancient Greek word , , "discourse", from , , "through" and , , "I speak") is used in two distinct ways ...
, exposure to noise, some
infection An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host A host is a person responsible for guests at an event or for providing hospitality during it. Host may ...

infection
s, birth complications, trauma to the ear, and certain medications or toxins. A common condition that results in hearing loss is
chronic ear infections Otitis media is a group of inflammatory diseases of the middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles, which trans ...
. Certain infections during pregnancy, such as
cytomegalovirus ''Cytomegalovirus'' (''CMV'') (from ''cyto-'' 'cell' via Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. I ...
,
syphilis Syphilis is a sexually transmitted infection Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs), are infection An infection is the invasion of an organism's body Tissue (biology), tissues ...
and
rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

rubella
, may also cause hearing loss in the child. Hearing loss is diagnosed when
hearing testing A hearing test provides an evaluation of the sensitivity of a person's sense of hearing Schematic diagram of the human ear Hearing, or auditory perception, is the ability to perceive Sound, sounds through an organ, such as an ear, by detecti ...
finds that a person is unable to hear 25
decibels The decibel (symbol: dB) is a relative unit of measurement A unit of measurement is a definite magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (ma ...
in at least one ear. Testing for poor hearing is recommended for all newborns. Hearing loss can be categorized as mild (25 to 40 ), moderate (41 to 55 dB), moderate-severe (56 to 70 dB), severe (71 to 90 dB), or profound (greater than 90 dB). There are three main types of hearing loss:
conductive hearing loss Conductive hearing loss (CHL) occurs when there is a problem transferring sound wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...
,
sensorineural hearing loss Sensorineural hearing loss (SNHL) is a type of hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In c ...
, and mixed hearing loss. About half of hearing loss globally is preventable through public health measures. Such practices include
immunization Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the antigen, immunogen). When this system is exposed to molecules that are foreign to the body, called ' ...

immunization
, proper care around
pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual repr ...

pregnancy
, avoiding loud noise, and avoiding certain medications. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unit ...
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. Early identification and support are particularly important in children. For many,
hearing aids A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. ...

hearing aids
,
sign language Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination with non-manual elements. Sign languages are full-fled ...

sign language
,
cochlear implants A cochlear implant (CI) is a surgically implanted Neuroprosthetics, neuroprosthesis that provides a person who has bilateral moderate-to-profound sensorineural hearing loss with sound perception and an opportunity with therapy for improved speech u ...
and
subtitles Subtitles are text Text may refer to: Written word * Text (literary theory) Text may refer to: Written word * Text (literary theory), any object that can be read, including: **Religious text, a writing that a religious tradition considers ...
are useful.
Lip reading Lip reading, also known as speechreading, is a technique of understanding speech Speech is human vocal communication using language. Each language uses Phonetics, phonetic combinations of vowel and consonant sounds that form the sound of its wor ...
is another useful skill some develop. Access to hearing aids, however, is limited in many areas of the world. As of 2013 hearing loss affects about 1.1 billion people to some degree. It causes disability in about 466 million people (5% of the global population), and moderate to severe disability in 124 million people. Of those with moderate to severe disability 108 million live in low and middle income countries. Of those with hearing loss, it began during childhood for 65 million. Those who use sign language and are members of
Deaf culture Deaf culture is the set of social beliefs, behaviors, art, literary traditions, history, values, and shared institutions of communities that are influenced by deafness Deafness has varying definitions in cultural and medical contexts. In ...
may see themselves as having a difference rather than a
disability A disability is any condition that makes it more difficult for a person to do certain activities or effectively interact with the world around them (socially or materially). These conditions, or impairments, may be Cognitive disability, cogn ...

disability
. Many members of Deaf culture oppose attempts to cure deafness and some within this community view cochlear implants with concern as they have the potential to eliminate their culture. The terms hearing impairment or hearing loss are often viewed negatively as emphasizing what people cannot do, although the terms are still regularly used when referring to deafness in medical contexts.


Definition

*Hearing loss is defined as diminished acuity to sounds which would otherwise be heard normally. The terms hearing impaired or hard of hearing are usually reserved for people who have relative inability to hear sound in the speech frequencies. 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. In profound deafness, even the highest intensity sounds produced by an
audiometer An audiometer is a machine used for evaluating hearing acuity. They usually consist of an embedded hardware unit connected to a pair of headphones Headphones are a pair of small Electrodynamic speaker driver, loudspeaker drivers worn on or a ...
(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. *
Speech perception Speech perception is the process by which the sounds of language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an apparent answer to th ...
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
auditory neuropathyAuditory neuropathy (AN) is a hearing disorder in which the outer hair cells of the cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axi ...
, 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.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 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.


Hearing standards

Human hearing extends in frequency from 20 to 20,000 Hz, and in intensity from 0 dB to 120 dB HL or more. 0 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 dB. Sound is generally uncomfortably loud above 90 dB and 115 dB represents the
threshold of pain The threshold of pain or pain threshold is the point along a curve In mathematics, a curve (also called a curved line in older texts) is an object similar to a line (geometry), line, but that does not have to be Linearity, straight. Intuitively, ...
. The ear does not hear all frequencies equally well: hearing sensitivity peaks around 3,000 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.


Signs and symptoms

*difficulty using the
telephone A telephone is a telecommunication Telecommunication is the transmission of information by various types of technologies over wire A wire is a single usually cylindrical A cylinder (from Greek Greek may refer to: Greece Anyt ...

telephone
*loss of
sound localization Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance. The sound localization mechanisms of the mammalian auditory system have been extensively studied. The auditory system us ...
*difficulty understanding speech, especially of children and women whose voices are of a higher frequency. *difficulty understanding speech in the presence of background noise (
cocktail party effect The cocktail party effect is the phenomenon of the brain's ability to focus one's auditory attention on a particular stimulus while filtering out a range of other stimuli, as when a partygoer can focus on a single conversation in a noisy room. List ...
) *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: *
hyperacusis Hyperacusis is a very rare and highly debilitating hearing, hearing disorder characterized by an increased sensitivity to certain Audio frequency, frequencies and Loudness, volume ranges of sound, or a lower than average tolerance for environmental ...
, heightened sensitivity with accompanying auditory pain to certain intensities and frequencies of sound, sometimes defined as " auditory recruitment" *
tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone will experience a faint "normal tinnitus" in a completely quiet room but it is only of concern if it is bothersome or interferes with normal h ...

tinnitus
, ringing, buzzing, hissing or other sounds in the ear when no external sound is present *
vertigo Vertigo is a condition where a person has the sensation of moving or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties wal ...

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 Bell's palsy


Complications

Hearing loss is associated with
Alzheimer's disease Alzheimer's disease (AD), also referred to simply as Alzheimer's, is a that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of . The most common early symptom is difficulty in . As the disease advance ...
and
dementia Dementia manifests as a set of related symptoms, which usually surface when the brain is damaged by injury or disease. The symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or ...
. 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. According to preliminary data,
hearing aid A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, soun ...
usage can slow down the decline in
cognitive functionsCognitive skills, also called cognitive functions, cognitive abilities or cognitive capacities, are brain-based skills which are needed in acquisition of knowledge, manipulation of information, and reasoning. They have more to do with the mechanisms ...
. Hearing loss is responsible for causing thalamocortical dysrthymia in the brain which is a cause for several neurological disorders including
tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone will experience a faint "normal tinnitus" in a completely quiet room but it is only of concern if it is bothersome or interferes with normal h ...

tinnitus
and .


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. 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
mild cognitive impairment Mild cognitive impairment (MCI) is a neurocognitive disorder which involves cognitive impairments beyond those expected based on an individual's age and education but which are not significant enough to interfere with instrumental activities of d ...
and eventually dementia. 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. 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. There are several hypothesis 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. Another possible cognitive mechanism emphasize on individual's
cognitive load In cognitive psychology Cognitive psychology is the scientific study of mental processes such as attention, language use, memory Memory is the faculty of the brain by which data or information is encoded, stored, and retrieved when needed. ...
. 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. One other hypothesis suggests that the association between hearing loss and cognitive decline is mediated through various psychosocial factors, such as decrease in social contact and increase in
social isolation Social isolation is a state of complete or near-complete lack of contact between an individual and society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social gro ...
. Findings on the association between hearing loss and dementia have significant public health implication, since about 9% of dementia cases can be attributed to hearing loss.


Falls

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. Fall-related injury can also lead to burdens on the financial and health care systems. In literature, age-related hearing loss is found to be significantly associated with incident falls. There is also a potential 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. 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
auditory system The auditory system is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neur ...
and increase in incident falls, driven by physiological, cognitive, and behavioral factors. This evidence suggests that treating hearing loss has potential to increase health-related quality of life in older adults.


Depression

Depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
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. 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 Coronary artery disease (CAD), also called coronary heart disease (CHD), Ischemia, ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the myocardium, heart muscle due to build-up of plaque (atherosclero ...
,
pulmonary disease Respiratory diseases, or lung diseases, are pathological Pathology is the study of the causes and effects of disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an ...
,
vision loss Visual impairment, also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses Glasses, also known as eyeglasses or spectacles, are vision eyew ...
and hearing loss. 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.


Spoken language ability

Post-lingual deafness is hearing loss that is sustained after the acquisition of language, which can occur due to
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interactin ...
,
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic injur ...
, 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. 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 A birth defect, also known as a congenital disorder, is a condition present at birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiate ...
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). 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
sign language Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination with non-manual elements. Sign languages are full-fled ...

sign language
and cannot competently provide it to their children without learning it themselves. Unfortunately, this may in some cases (late implantation or not sufficient benefit from cochlear implants) bring the risk of
language deprivationLanguage deprivation is associated with the lack of linguistic stimuli that are necessary for the language acquisition Language acquisition is the process by which humans acquire the capacity to perceive and comprehend language A language i ...
for the deaf baby 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.


Causes

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
presbycusis Presbycusis (also spelled presbyacusis, from Greek ''presbys'' "old" + ''akousis'' "hearing"), or age-related hearing loss, is the cumulative effect of aging on Hearing (sense), hearing. It is a progressive and irreversible bilateral symmetrical ag ...
. 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. 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. While everyone loses hearing with age, the amount and type of hearing loss is variable.
Noise-induced hearing loss Noise-induced hearing loss (NIHL) is hearing impairment Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, he ...
(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. The majority of hearing loss is not due to age, but due to noise exposure. Various governmental, industry and standards organizations set noise standards. 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. 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. Hearing loss in adolescents may be caused by loud noise from toys, music by headphones, and concerts or events. 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 Sex linked describes the sex-specific patterns of Heredity, inheritance and Phenotype, presentation when a gene mutation (allele) is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). In humans, these are termed ...
patterns, and fewer than 1% are inherited by
mitochondrial inheritance File:Electron microscopy reveals mitochondrial DNA in discrete foci.jpg, Electron microscopy reveals mitochondrial DNA in discrete foci. Bars: 200 nm. (A) Cytoplasmic section after immunogold labelling with anti-DNA; gold particles marking mtDNA ...

mitochondrial inheritance
. Syndromic deafness occurs when there are other signs or medical problems aside from deafness in an individual, such as
Usher syndrome Usher syndrome, also known as Hallgren syndrome, Usher–Hallgren syndrome, retinitis pigmentosa–dysacusis syndrome or dystrophia retinae dysacusis syndrome, is a rare genetic disorder A genetic disorder is a health problem caused by one o ...
, Stickler syndrome,
Waardenburg syndrome Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or Heterochromia iridum, one blue eye and one brown ey ...

Waardenburg syndrome
,
Alport's syndrome Alport syndrome is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen co ...
, and
neurofibromatosis type 2 Neurofibromatosis type II (also known as MISME syndrome – multiple inherited schwannomas, meningiomas, and ependymomas) is a genetic condition which may be inherited or may arise spontaneously. The main manifestation of the condition is the dev ...
. Nonsyndromic deafness occurs when there are no other signs or medical problems associated with the deafness in an individual.
Fetal alcohol spectrum disorder Fetal alcohol spectrum disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol during pregnancy. Symptoms can include an abnormal appearance, short height, low body weight, small head size, poor coordi ...
s are reported to cause hearing loss in up to 64% of infants born to
alcoholic Alcoholism is, broadly, any drinking of alcohol (drug), alcohol that results in significant Mental health, mental or physical health problems. Alcoholism is not a recognized diagnostic entity. Predominant diagnostic classifications are alcoho ...
mothers, from the ototoxic effect on the developing fetus plus malnutrition during pregnancy from the excess
alcohol In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a Saturated and unsaturated compounds, saturated carbon atom. The term alcohol originally referred to the primary alcohol ethan ...

alcohol
intake.
Premature birth Preterm birth, also known as premature birth, is the birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause ...

Premature birth
can be associated with sensorineural hearing loss because of an increased risk of hypoxia,
hyperbilirubinaemia Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera, whites of the eyes due to hyperbilirubinemia, high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying dis ...
, 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. The risk of hearing loss is greatest for those weighing less than 1500 g at birth. Disorders responsible for hearing loss include
auditory neuropathyAuditory neuropathy (AN) is a hearing disorder in which the outer hair cells of the cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axi ...
,
Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology and genetics Gen ...
,
Charcot–Marie–Tooth disease Charcot–Marie–Tooth disease (CMT) is a hereditary motor and sensory neuropathy of the peripheral nervous system characterized by progressive loss of muscle tissue and touch sensation across various parts of the body. This disease is the most ...
variant 1E,
autoimmune disease An autoimmune disease is a condition arising from an abnormal immune response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of differe ...

autoimmune disease
,
multiple sclerosis Multiple sclerosis (MS), also known as encephalomyelitis disseminata, is the most common demyelinating disease, in which the Myelin, insulating covers of nerve cells in the Human brain, brain and spinal cord are damaged. This damage disrupts the ...
,
meningitis Meningitis is an acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is of short dur ...
,
cholesteatoma Cholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process. Cholesteatomas are not cancerous as the name may suggest, but can cause significant problems because of th ...
,
otosclerosis Otosclerosis is a condition of the middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles, which transfer the vibrations of ...
, perilymph fistula,
Ménière's disease Ménière's disease (MD) is a disorder of the inner ear that is characterized by episodes of vertigo, tinnitus, hearing loss, and a fullness in the ear. Typically, only one ear is affected initially; however, over time both ears may become invo ...
, recurring ear infections, strokes, superior semicircular canal dehiscence, Pierre Robin, Treacher-Collins,
Usher Syndrome Usher syndrome, also known as Hallgren syndrome, Usher–Hallgren syndrome, retinitis pigmentosa–dysacusis syndrome or dystrophia retinae dysacusis syndrome, is a rare genetic disorder A genetic disorder is a health problem caused by one o ...
, Pendred Syndrome, and
Turner Turner may refer to: People and fictional characters * Turner (surname), a common surname, including a list of people and fictional characters with the name * Turner (given name), a list of people with the given name *One who uses a lathe for turni ...
syndrome,
syphilis Syphilis is a sexually transmitted infection Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs), are infection An infection is the invasion of an organism's body Tissue (biology), tissues ...
,
vestibular schwannoma A vestibular schwannoma (VS) is a benign primary intracranial tumor of the myelin Myelin is a lipid-rich (fatty) substance that surrounds nerve cell axons (the nervous system's "wires") to Insulator (electricity), insulate them and increase ...
, and
viral infections A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characteristics Basic structural charact ...

viral infections
such as
measles Measles is a highly contagious infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to ...
,
mumps Mumps is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characterist ...

mumps
, congenital
rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

rubella
(also called German measles) syndrome, several varieties of herpes viruses,
HIV/AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of ...
, and
West Nile virus West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family ''Flaviviridae'', from the genus ''Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The virus i ...
. Some medications may reversibly affect hearing. These medications are considered
ototoxic Ototoxicity is the property of being toxicity, toxic to the ear (''oto-''), specifically the cochlea or vestibulocochlear nerve, auditory nerve and sometimes the vestibular system, for example, as a side effect of a drug. The effects of ototoxicity ...
. This includes
loop diuretic Loop diuretics are diuretic A diuretic () is any substance that promotes diuresis Diuresis () is increased urination Urination is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the uri ...
s such as furosemide and bumetanide,
non-steroidal anti-inflammatory drug Nonsteroidal anti-inflammatory drugs (NSAIDs) are members of a drug class A drug is any chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass a ...
s (NSAIDs) both over-the-counter (aspirin, ibuprofen, naproxen) as well as prescription (celecoxib, diclofenac, etc.), paracetamol,
quinine Quinine is a medication used to treat malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms Signs and symptoms are the observed or detectable signs, and experienced sympto ...

quinine
, and
macrolide antibiotics. The macrolide ring is the lactone (cyclic ester) at upper-left. Image:Roxithromycin.svg, 150px, Roxithromycin The macrolides are a class of natural products that consist of a large macrocycle, macrocyclic lactone ring to which one or more deoxy ...
. Others may cause permanent hearing loss. The most important group is the
aminoglycoside Aminoglycoside is a medicinal chemistry, medicinal and bacteriology, bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside ( ...
s (main member
gentamicin Gentamicin, sold under brand name Garamycin among others, is an antibiotic An antibiotic is a type of antimicrobial substance active against bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology ...

gentamicin
) and platinum based chemotherapeutics such as
cisplatin Cisplatin is a chemotherapy medication used to treat a number of cancers. These include testicular cancer, ovarian cancer Ovarian cancer is a cancer Cancer is a group of diseases involving abnormal cell growth with the potential to i ...

cisplatin
and
carboplatin Carboplatin, sold under the trade name Paraplatin among others, is a chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agen ...
. In addition to medications, hearing loss can also result from specific chemicals in the environment: metals, such as
lead Lead is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elements ...

lead
;
solvents A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...
, such as
toluene Toluene (), also known as toluol (), is an aromatic hydrocarbon. It is a colorless, Water (molecule), water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group ( ...

toluene
(found in
crude oil Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mech ...
,
gasoline Gasoline () or petrol () (see the etymology Etymology ()The New Oxford Dictionary of English ''The'' () is a grammatical article Article often refers to: * Article (grammar) An article is any member of a class of dedicated word ...

gasoline
and automobile exhaust, for example); and asphyxiants. Combined with noise, these ototoxic chemicals have an additive effect on a person's hearing loss. Hearing loss due to chemicals starts in the high frequency range and is irreversible. It damages the
cochlea The cochlea is the part of the inner ear Inner Ear (established in 2007 in Bodø, Norway) is a Norwegian record label initiated and led by the brothers and jazz musicians Tore Johansen and Roger Johansen (musician), Roger Johansen. They opene ...

cochlea
with lesions and degrades central portions of the
auditory system The auditory system is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neur ...
. For some ototoxic chemical exposures, particularly styrene, the risk of hearing loss can be higher than being exposed to
noise Noise is unwanted sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and t ...

noise
alone. The effects is greatest when the combined exposure include impulse noise. A 2018 informational bulletin by the US
Occupational Safety and Health Administration The Occupational Safety and Health Administration (OSHA ) is a large regulatory agency of the United States Department of Labor The United States Department of Labor (DOL) is a cabinet-level department of the U.S. federal government, re ...
(OSHA) and the
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury Injury, also known as physical ...
(NIOSH) introduces the issue, provides examples of ototoxic chemicals, lists the industries and occupations at risk and provides prevention information. 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 . People who sustain head injury are especially vulnerable to hearing loss or tinnitus, either temporary or permanent.


Pathophysiology

Sound waves reach the outer ear and are conducted down the ear canal to the
eardrum In the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, ...
, causing it to vibrate. The vibrations are transferred by the 3 tiny ear bones of the
middle ear The middle ear is the portion of the ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is t ...

middle ear
to the fluid in the inner ear. The fluid moves hair cells (
stereocilia Stereocilia (or stereovilli) are non-motile apical modifications of the cell. They are distinct from cilia The cilium (; the plural is cilia) is an organelle found on eukaryotic cells in the shape of a slender protuberance that projects from the ...

stereocilia
), and their movement generates nerve impulses which are then taken to the brain by the
cochlear nerve The cochlear nerve (also auditory or acoustic neuron) is one of two parts of the vestibulocochlear nerve The vestibulocochlear nerve (auditory vestibular nerve), known as the eighth cranial nerve, transmits sound and equilibrium (balance) informa ...
. 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. 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. 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.


Diagnosis

Identification of a hearing loss is usually conducted by a general practitioner
medical doctor A physician (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American Eng ...

medical doctor
,
otolaryngologist Otorhinolaryngology ( ; abbreviated ORL; also called otolaryngology; other terms include otolaryngology–head and neck surgery (ORL–H&N, OHNS) and ear, nose, and throat, often called ENT) is a surgical subspecialty within medicine that de ...
, certified and licensed
audiologist Audiology (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...
, 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 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 hearing test using a mobile application or hearing aid application, which includes a hearing test. Hearing diagnosis using mobile application is similar to the audiometry procedure. Audiograms, obtained using mobile applications, can be used to adjust hearing aid applications. 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. 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, tympanometry, and differential testing with the Weber test, Weber, Rinne test, Rinne, Bing test, Bing and Schwabach test, 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 decibels of hearing loss, or dB HL. There are three main ''types'' of hearing loss:
conductive hearing loss Conductive hearing loss (CHL) occurs when there is a problem transferring sound wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...
,
sensorineural hearing loss Sensorineural hearing loss (SNHL) is a type of hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In c ...
, and mixed hearing loss. An additional problem which is increasingly recognised is 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.


Prevention

It is estimated that half of cases of hearing loss are preventable. About 60% of hearing loss in children under the age of 15 can be avoided. There are a number of effective preventative strategies, including: immunization against
rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

rubella
to prevent congenital rubella syndrome, immunization against ''H. influenza'' and ''S. pneumoniae'' to reduce cases of
meningitis Meningitis is an acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is of short dur ...
, and avoiding or protecting against excessive noise exposure. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unit ...
also recommends immunization against
measles Measles is a highly contagious infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to ...
,
mumps Mumps is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characterist ...

mumps
, and
meningitis Meningitis is an acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is of short dur ...
, efforts to prevent premature birth, and avoidance of certain medication as prevention. World Hearing Day is a yearly event to promote actions to prevent hearing damage. Noise exposure is the most significant risk factor for noise-induced hearing loss that can be prevented. Different programs exist for specific populations such as school-age children, adolescents and workers. Education regarding noise exposure increases the use of hearing protectors. The use of antioxidants 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.


Workplace noise regulation

Noise is widely recognized as an occupational hazard. In the United States, the
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury Injury, also known as physical ...
(NIOSH) and the
Occupational Safety and Health Administration The Occupational Safety and Health Administration (OSHA ) is a large regulatory agency of the United States Department of Labor The United States Department of Labor (DOL) is a cabinet-level department of the U.S. federal government, re ...
(OSHA) work together to provide standards and enforcement on workplace noise levels. The hierarchy of hazard controls demonstrates the different levels of controls to reduce or eliminate exposure to noise and prevent hearing loss, including engineering controls and personal protective equipment (PPE). Other programs and initiative have been created to prevent hearing loss in the workplace. For example, the Safe-In-Sound Award, Safe-in-Sound Award was created to recognize organizations that can demonstrate results of successful noise control and other interventions. Additionally, the Buy Quiet program was created to encourage employers to purchase quieter machinery and tools. By purchasing less noisy power tools like those found on the NIOSH Power Tools Database and limiting exposure to ototoxic chemicals, great strides can be made in preventing hearing loss. 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. Often interventions to prevent noise-induced hearing loss have many components. A 2017 Cochrane review found that stricter legislation might reduce noise levels. 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. 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 Sound exposure, noise exposure. The result is calculated via an 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.


Screening

The United States Preventive Services Task Force recommends Universal neonatal hearing screening, neonatal hearing screening for all newborns. The American Academy of Pediatrics advises that children should have their hearing tested several times throughout their schooling: *When they enter preschool, school *At ages 6, 8, and 10 *At least once during middle school *At least once during High school (North America), 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, the American Speech–Language–Hearing Association, 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. For the same reason, the US Office of Disease Prevention and Health Promotion included as one of Healthy People program, Healthy People 2020 objectives: to increase the proportion of persons who have had a hearing examination.


Management

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 and underlying nerve problem may be treated with corticosteroids. 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
hearing aid A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, soun ...
s, cochlear implants, assistive technology, and closed captioning. 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. 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).


Epidemiology

Globally, hearing loss affects about 10% of the population to some degree. It caused moderate to severe disability in 124.2 million people as of 2004 (107.9 million of whom are in low and middle income countries). Of these 65 million acquired the condition during childhood. At birth ~3 per 1000 in developed countries and more than 6 per 1000 in developing countries have hearing problems. 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%. 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. Globally, the annual cost of unaddressed hearing loss was estimated to be in the range of $750–790 billion International Dollars, international dollars. The International Organization for Standardization (ISO) developed the ISO 1999 standards for the estimation of hearing thresholds and noise-induced hearing impairment. 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). 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, Norway, South Korea, the United States and Spain. In the United States hearing is one of the health outcomes measure by the National Health and Nutrition Examination Survey (NHANES), a Statistical survey, survey research program conducted by the National Center for Health Statistics. It examines health and nutritional status of adults and children in the 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. 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.


Social and cultural aspects

People with extreme hearing loss may communicate through
sign language Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Sign languages are expressed through manual articulations in combination with non-manual elements. Sign languages are full-fled ...

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".
Deaf culture Deaf culture is the set of social beliefs, behaviors, art, literary traditions, history, values, and shared institutions of communities that are influenced by deafness Deafness has varying definitions in cultural and medical contexts. In ...
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," an example being 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. Members of the Deaf community tend to view deafness as a difference in human experience rather than a
disability A disability is any condition that makes it more difficult for a person to do certain activities or effectively interact with the world around them (socially or materially). These conditions, or impairments, may be Cognitive disability, cogn ...

disability
or
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interactin ...
. 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 D Deaf" in speech and sign. When used as a label for the Audiology, audiological condition, it is written with a lower case ''d''. 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 National Technical Institute for the Deaf in the USA, and the National University Corporation Tsukuba University of Technology, National University Corporation of Tsukuba University of Technology in Japan.


Research


Stem cell transplant and gene therapy

A 2005 study achieved successful regrowth of cochlea cells in guinea pigs. 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 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. Recent research, reported in 2012 achieved growth of cochlear nerve cells resulting in hearing improvements in gerbils, using stem cells. Also reported in 2013 was regrowth of hair cells in deaf adult mice using a drug intervention resulting in hearing improvement. The Hearing Health Foundation in the US has embarked on a project called the Hearing Restoration Project. Also Action on Hearing Loss in the UK is also aiming to restore hearing. Researchers reported in 2015 that genetically deaf mice which were treated with TMC1 gene therapy recovered some of their hearing. In 2017, additional studies were performed to treat
Usher syndrome Usher syndrome, also known as Hallgren syndrome, Usher–Hallgren syndrome, retinitis pigmentosa–dysacusis syndrome or dystrophia retinae dysacusis syndrome, is a rare genetic disorder A genetic disorder is a health problem caused by one o ...
and here, a recombinant adeno-associated virus seemed to outperform the older vectors.


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.


See also

*H.870 *Safe listening


References


External links

*
National Institute for the Prevention of Deafness and other Communication Disorders
* World Health Organization Composite International Diagnostic Interview, World Health Organization
Global Costs of unaddressed hearing loss and cost-effectiveness of interventions, 2017

World Health Organization, Deafness and Hearing LossWorld Report on Hearing
World Health Organization, 2021. *

(NIOSH) * OSHA-NIOSH 2018. doi:10.26616/NIOSHPUB2018124, Preventing Hearing Loss Caused by Chemical (Ototoxicity) and Noise Exposure Safety and Health Information Bulletin (SHIB), Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health.  SHIB 03-08-2018. DHHS (NIOSH) Publication No. 2018-124. * Centers for Disease Control and Prevention Vital Signs- Hearing Los
Loud Noises Damage Hearing
* {{Authority control Hearing loss, Audiology Communication disorders Occupational safety and health Otorhinolaryngology Wikipedia medicine articles ready to translate Wikipedia neurology articles ready to translate Deafness