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, hearing problems can affect the ability to ]acquire
''Acquire'' is a multi-player mergers and acquisitions themed board game. It is played with tiles representing hotels that are arranged on the board, play money and stock certificates. The object of the game is to earn the most money by developi ...
spoken language
Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of ...
, 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 and the vestibular system in the ears of all vertebrates, and in the lateral line organ of fishes. Through mechanotransduction, hair cells detect movement in their environment. ...
loss. In some people, particularly older people, hearing loss can result in loneliness.[ Deaf people usually have little to no hearing.]
Hearing loss may be caused by a number of factors, including: genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
, ageing, exposure to noise, some infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...
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. One of the two main types is acute otitis media (AOM), an infection of rapid onset that usually presents with ear pain. In young children this may result in pulling at the ear, ...
.[ Certain infections during pregnancy, such as cytomegalovirus, syphilis and 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 and is most often performed by an audiologist using an audiometer. An audiometer is used to determine a person's hearing sensitivity at different frequencies ...
finds that a person is unable to hear 25 decibels in at least one ear.[ Testing for poor hearing is recommended for all newborns.][ Hearing loss can be categorized as mild (25 to 40 dB), 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 waves anywhere along the pathway through the outer ear, tympanic membrane (eardrum), or middle ear (ossicles). If a conductive hearing loss occurs in conjunction with ...
, sensorineural hearing loss, 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 immunogen).
When this system is exposed to molecules that are foreign to the body, called ''non-se ...
, proper care around pregnancy
Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occur ...
, avoiding loud noise, and avoiding certain medications.[ The ]World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
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 aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers su ...
, sign language
Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning, instead of spoken words. Sign languages are expressed through manual articulation in combination with non-manual markers. Sign l ...
, cochlear implants
A cochlear implant (CI) is a surgically implanted neuroprosthesis that provides a person who has moderate-to-profound sensorineural hearing loss with sound perception. With the help of therapy, cochlear implants may allow for improved speech unde ...
and subtitles are useful.[ ]Lip reading
The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...
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 may see themselves as having a difference rather than a disability
Disability is the experience of any condition that makes it more difficult for a person to do certain activities or have equitable access within a given society. Disabilities may be cognitive, developmental, intellectual, mental, physical, ...
.[ 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 and a test subject feedback button, sometimes controlled by a standard PC. Such systems can also be ...
(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 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 neuropathy Auditory neuropathy (AN) is a hearing disorder in which the outer hair cells of the cochlea are present and functional, but sound information is not transmitted sufficiently by the auditory nerve to the brain. Hearing loss with AN can range from nor ...
, 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 of increasing perception of a stimulus at which pain begins to be felt. It is an entirely subjective phenomenon. A distinction must be maintained between the stimulus (an external ...
. 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 telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...
* 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, such as when a partygoer can focus on a single conversation in a noisy roo ...
)
* 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 the increased sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly; it can refer to normal noises being perceived as: loud, annoying, painful, fear-inducing, or a combina ...
, 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 experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...
, 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 movement 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 w ...
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 and dementia
Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
. 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 aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers s ...
usage can slow down the decline in cognitive functions
Cognitive 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 experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...
and visual snow syndrome.
Cognitive decline
Hearing loss is an increasing concern especially in aging populations. The prevalence of hearing loss increases about two-fold for each decade increase in age after age 40. 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 o ...
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 load refers to the amount of working memory resources used. There are three types of cognitive load: ''intrinsic'' cognitive load is the effort associated with a specific topic; ''extraneous'' cognitive load refe ...
. 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. It differs from loneliness, which reflects temporary and involuntary lack of contact with other humans in the world. Social isolation ...
. Findings on the association between hearing loss and dementia have significant public health implication, since about 9% of dementia cases are associated with hearing loss.
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 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 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), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic pl ...
, pulmonary disease
Respiratory diseases, or lung diseases, are pathological conditions affecting the organs and tissues that make gas exchange difficult in air-breathing animals. They include conditions of the respiratory tract including the trachea, bronchi, bron ...
, vision loss
Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment ...
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 or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
, 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 i ...
, 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 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, instead of spoken words. Sign languages are expressed through manual articulation in combination with non-manual markers. Sign l ...
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 deprivation 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 πρέσβυς ''presbys'' "old" + ἄκουσις ''akousis'' "hearing"), or age-related hearing loss, is the cumulative effect of aging on hearing. It is a progressive and irreversible bilateral ...
. 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 a hearing impairment resulting from exposure to loud sound. People may have a loss of perception of a narrow range of frequencies or impaired perception of sound including sensitivity to sound or ringing i ...
(NIHL), also known as acoustic trauma
Acoustic trauma is the sustainment of an injury to the eardrum as a result of a very loud noise. Its scope usually covers loud noises with a short duration, such as an explosion, gunshot or a burst of loud shouting. Quieter sounds that are concentr ...
, 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 inheritance and 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 X-linked recessive, ...
patterns, and fewer than 1% are inherited by mitochondrial inheritance
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...
. 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 caused by a mutation in any one of at least 11 genes result ...
, 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 one blue eye and one brown eye), a white foreloc ...
, Alport's syndrome, and neurofibromatosis type 2. Nonsyndromic deafness
Nonsyndromic deafness is hearing loss that is not associated with other signs and symptoms. In contrast, syndromic deafness involves hearing loss that occurs with abnormalities in other parts of the body. Genetic changes are related to the follow ...
occurs when there are no other signs or medical problems associated with the deafness in an individual.
Fetal alcohol spectrum disorders are reported to cause hearing loss in up to 64% of infants born to alcoholic
Alcoholism is, broadly, any drinking of alcohol that results in significant mental or physical health problems. Because there is disagreement on the definition of the word ''alcoholism'', it is not a recognized diagnostic entity. Predomina ...
mothers, from the ototoxic effect on the developing fetus plus malnutrition during pregnancy from the excess alcohol intake. Premature birth
Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between 2 ...
can be associated with sensorineural hearing loss because of an increased risk of hypoxia, hyperbilirubinaemia, ototoxic medication and infection as well as noise exposure in the neonatal units. Also, hearing loss in premature babies is often discovered far later than a similar hearing loss would be in a full-term baby because normally babies are given a hearing test within 48 hours of birth, but doctors must wait until the premature baby is medically stable before testing hearing, which can be months after birth. The risk of hearing loss is greatest for those weighing less than 1500 g at birth.
Disorders responsible for hearing loss include auditory neuropathy Auditory neuropathy (AN) is a hearing disorder in which the outer hair cells of the cochlea are present and functional, but sound information is not transmitted sufficiently by the auditory nerve to the brain. Hearing loss with AN can range from nor ...
, Down syndrome
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...
, 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, multiple sclerosis, meningitis, 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 where portions of the dense enchondral layer of the bony labyrinth remodel into one or more lesions of irregularly-laid spongy bone. As the lesions reach the stapes the bone is resorbed, then har ...
, perilymph fistula, Ménière's disease
Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected initi ...
, 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 caused by a mutation in any one of at least 11 genes result ...
, Pendred Syndrome
Pendred syndrome is a genetic disorder leading to congenital bilateral (both sides) sensorineural hearing loss and goitre with euthyroid or mild hypothyroidism (decreased thyroid gland function). There is no specific treatment, other than suppo ...
, 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, vestibular schwannoma
A vestibular schwannoma (VS), also called acoustic neuroma, is a benign tumor that develops on the vestibulocochlear nerve that passes from the inner ear to the brain. The tumor originates when Schwann cells that form the insulating myelin sheath ...
, and viral infections
A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells.
Structural Characteristics
Basic structural characteristics, ...
such as measles, mumps, congenital 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 with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual ...
, 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 v ...
.
Some medications may reversibly affect hearing. These medications are considered ototoxic
Ototoxicity is the property of being toxic to the ear (''oto-''), specifically the cochlea or auditory nerve and sometimes the vestibular system, for example, as a side effect of a drug. The effects of ototoxicity can be reversible and temporary, ...
. This includes loop diuretic
Loop diuretics are diuretics that act on the Na-K-Cl cotransporter along the thick ascending limb of the loop of Henle in the kidney. They are primarily used in medicine to treat hypertension and edema often due to congestive heart failure ...
s such as furosemide and bumetanide, non-steroidal anti-inflammatory drug
Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...
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 and babesiosis. This includes the treatment of malaria due to '' Plasmodium falciparum'' that is resistant to chloroquine when artesunate is not available. While sometimes used for nocturnal le ...
, and macrolide antibiotics
The Macrolides are a class of natural products that consist of a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. Mac ...
. Others may cause permanent hearing loss. The most important group is the aminoglycoside
Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside (sugar). The term can also refer ...
s (main member 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, cervical cancer, breast cancer, bladder cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, ...
and carboplatin
Carboplatin, sold under the trade name Paraplatin among others, is a chemotherapy medication used to treat a number of forms of cancer. This includes ovarian cancer, lung cancer, head and neck cancer, brain cancer, and neuroblastoma. It is used b ...
.
In addition to medications, hearing loss can also result from specific chemicals in the environment: metals, such as lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
; solvents, such as toluene
Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) a ...
(found in crude oil, gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organi ...
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 involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory or ...
with lesions and degrades central portions of the auditory system. For some ototoxic chemical exposures, particularly styrene, the risk of hearing loss can be higher than being exposed to noise
Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference aris ...
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 that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(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 and illness. NIOSH is part of the C ...
(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 temporal bone fracture. 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, 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 medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear).
The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...
to the fluid in the inner ear. The fluid moves hair cells (stereocilia
Stereocilia (or stereovilli or villi) are non-motile apical cell modifications. They are distinct from cilia and microvilli, but are closely related to microvilli. They form single "finger-like" projections that may be branched, with normal cell ...
), and their movement generates nerve impulses which are then taken to the brain by the cochlear nerve
The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve. The cochlear nerve carries auditory sensory informatio ...
. 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, otolaryngologist
Otorhinolaryngology ( , abbreviated ORL and also known as otolaryngology, otolaryngology–head and neck surgery (ORL–H&N or OHNS), or ear, nose, and throat (ENT)) is a surgical subspeciality within medicine that deals with the surgical a ...
, certified and licensed audiologist
Audiology (from Latin , "to hear"; and from Greek , ''-logia'') is a branch of science that studies hearing, balance, and related disorders. Audiologists treat those with hearing loss and proactively prevent related damage. By employing vario ...
, school or industrial audiometrist
An Audiometrist (from Latin , "to hear"; and from Italian '' -metria'', “to measure” ) or Audiometric Officer, is a health-care professional technician who has received special training in the use of Pure tone audiometry equipment. An audiometr ...
, 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
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
of sounds. To take this into account, hearing sensitivity can be measured for a range of frequencies and plotted on an audiogram
An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer. The Y axis represents intensity measured in decibels and the X axis represents frequency measured in hertz. The threshold of hea ...
. Other method for quantifying hearing loss is a hearing test
A hearing test provides an evaluation of the sensitivity of a person's sense of hearing and is most often performed by an audiologist using an audiometer. An audiometer is used to determine a person's hearing sensitivity at different frequencies ...
using a mobile application or hearing aid application, which includes a hearing test. Hearing diagnosis using mobile application is similar to the audiometry
Audiometry () is a branch of audiology and the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, involving thresholds and differing frequencies. Typically, audiometric tests determine a subje ...
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
An otoscope or auriscope is a medical device which is used to look into the ears. Health care providers use otoscopes to screen for illness during regular check-ups and also to investigate ear symptoms. An otoscope potentially gives a view o ...
, tympanometry
Tympanometry is an acoustic evaluation of the condition of the middle ear eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal.
Tympanometry is an objective test of middle-ear function. It is ...
, and differential testing with the Weber, Rinne, Bing
Bing most often refers to:
* Bing Crosby (1903–1977), American singer
* Microsoft Bing, a web search engine
Bing may also refer to:
Food and drink
* Bing (bread), a Chinese flatbread
* Bing (soft drink), a UK brand
* Bing cherry, a varie ...
and Schwabach
Schwabach () is a German city of about 40,000 inhabitants near Nuremberg in the centre of the region of Franconia in the north of Bavaria. The city is an autonomous administrative district (''kreisfreie Stadt''). Schwabach is also the name of th ...
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 waves anywhere along the pathway through the outer ear, tympanic membrane (eardrum), or middle ear (ossicles). If a conductive hearing loss occurs in conjunction with ...
, sensorineural hearing loss, and mixed hearing loss. An additional problem which is increasingly recognised is auditory processing disorder
Auditory processing disorder (APD), rarely known as King-Kopetzky syndrome or auditory disability with normal hearing (ADN), is a neurodevelopmental disorder affecting the way the brain processes auditory information. Individuals with APD usually ...
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
A schwannoma (or neurilemmoma) is a usually benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves.
Schwannomas are homogeneous tumors, consisting only of Schwann cells ...
or other tumor.
People with unilateral hearing loss
Unilateral hearing loss (UHL) is a type of hearing impairment where there is normal hearing in one ear and impaired hearing in the other ear.
Signs and symptoms
Patients with unilateral hearing loss have difficulty:
* Hearing conversation on thei ...
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 to prevent congenital rubella syndrome
Congenital rubella syndrome (CRS) can occur in a developing fetus of a pregnant woman who has contracted rubella, usually in the first trimester. If infection occurs 0–28 days before conception, the infant has a 43% risk of being affected. If t ...
, immunization against '' H. influenza'' and '' S. pneumoniae'' to reduce cases of meningitis, 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 responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
also recommends immunization against measles, mumps, and meningitis, efforts to prevent premature birth
Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between 2 ...
, and avoidance of certain medication as prevention. World Hearing Day is a yearly event to promote actions to prevent hearing damage.
Avoiding exposure to loud noise can help prevent noise-induced hearing loss. 18% of adults exposed to loud noise at work for five years or more report hearing loss in both ears as compared to 5.5% of adults who were not exposed to loud noise at work. 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
An occupational hazard is a hazard experienced in the workplace. This encompasses many types of hazards, including chemical hazards, biological hazards (biohazards), psychosocial hazards, and physical hazards. In the United States, the Nation ...
. 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 and illness. NIOSH is part of the C ...
(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 that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) work together to provide standards and enforcement on workplace noise levels. The s demonstrates the different levels of controls to reduce or eliminate exposure to noise and prevent hearing loss, including engineering controls
Engineering controls are strategies designed to protect workers from hazardous conditions by placing a barrier between the worker and the hazard or by removing a hazardous substance through air ventilation. Engineering controls involve a physi ...
and personal protective equipment
Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, e ...
(PPE). Other programs and initiative have been created to prevent hearing loss in the workplace. For example, the Safe-in-Sound Award
The Safe-in-Sound Excellence in Hearing Loss Prevention Award is an occupational health and safety award that was established in 2007 through a partnership between the National Institute for Occupational Safety and Health (NIOSH) and the National ...
was created to recognize organizations that can demonstrate results of successful noise control and other interventions. Additionally, the Buy Quiet
Buy Quiet is an American health and safety initiative to select and purchase the lowest noise emitting power tools and machinery in order to reduce occupational and community noise exposure. Buy Quiet Programs are examples of noise control strategi ...
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
The NIOSH Power Tools Database contains sound power levels, sound pressure levels, and vibrations data for a variety of common power tools that have been tested by researchers. Data are collected for both the unloaded and loaded use of power tools ...
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 level
Sound exposure is the integral, over time, of squared sound pressure. The SI unit of sound exposure is the pascal squared second (Pa2·s).
Mathematical definition
Sound exposure, denoted ''E'', is defined by
:E = \int_^ p(t)^2\, \mathrmt,
where
*t ...
s 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 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 noise exposure. The result is calculated via an algebraic equation
In mathematics, an algebraic equation or polynomial equation is an equation of the form
:P = 0
where ''P'' is a polynomial with coefficients in some field, often the field of the rational numbers. For many authors, the term ''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
The United States Preventive Services Task Force (USPSTF) is "an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services". ...
recommends 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 school
A school is an educational institution designed to provide learning spaces and learning environments for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is sometimes comp ...
* At ages 6, 8, and 10
* At least once during middle school
A middle school (also known as intermediate school, junior high school, junior secondary school, or lower secondary school) is an educational stage which exists in some countries, providing education between primary school and secondary school. ...
* At least once during high school
A secondary school describes an institution that provides secondary education and also usually includes the building where this takes place. Some secondary schools provide both '' lower secondary education'' (ages 11 to 14) and ''upper seconda ...
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 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 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 an 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 aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers s ...
s, cochlear implant
A cochlear implant (CI) is a surgically implanted neuroprosthesis that provides a person who has moderate-to-profound sensorineural hearing loss with sound perception. With the help of therapy, cochlear implants may allow for improved speech unde ...
s, middle ear implant A middle ear implant is a hearing device that is surgically implanted into the middle ear. They help people with conductive, sensorineural or mixed hearing loss to hear.
Middle ear implants work by improving the conduction of sound vibrations fr ...
s, assistive technology, and closed captioning
Closed captioning (CC) and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information. Both are typically used as a transcription of the audio po ...
. 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
A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...
and more than 6 per 1000 in developing countries
A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreem ...
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 $750–790 billion ]international dollars
The international dollar (int'l dollar or intl dollar, symbols Int'l$., Intl$., Int$), also known as Geary–Khamis dollar (symbols G-K$ or GK$), is a hypothetical unit of currency that has the same purchasing power parity that the U.S. dollar ...
.
The International Organization for Standardization
The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Art ...
(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
The National Health and Nutrition Examination Survey (NHANES) is a survey research program conducted by the National Center for Health Statistics (NCHS) to assess the health and nutritional status of adults and children in the United States, and t ...
(NHANES), a survey
Survey may refer to:
Statistics and human research
* Statistical survey, a method for collecting quantitative information about items in a population
* Survey (human research), including opinion polls
Spatial measurement
* Surveying, the techniq ...
research
Research is " creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness ...
program conducted by the National Center for Health Statistics. It examines health
Health, according to the World Health Organization, is "a state of complete physical, mental and social well-being and not merely the absence of disease and infirmity".World Health Organization. (2006)''Constitution of the World Health Organiza ...
and nutrition
Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient ...
al status of adults and children in the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
. 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, instead of spoken words. Sign languages are expressed through manual articulation in combination with non-manual markers. Sign l ...
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 refers to a tight-knit cultural group
Cultural identity is a part of a person's identity, or their self-conception and self-perception, and is related to nationality, ethnicity, religion, social class, generation, locality or any kind of social group that has its own distinct cultur ...
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 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
Disability is the experience of any condition that makes it more difficult for a person to do certain activities or have equitable access within a given society. Disabilities may be cognitive, developmental, intellectual, mental, physical, ...
or disease
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
. 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 audiological
Audiology (from Latin , "to hear"; and from Greek , ''-logia'') is a branch of science that studies hearing, balance, and related disorders. Audiologists treat those with hearing loss and proactively prevent related damage. By employing various ...
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
The National Technical Institute for the Deaf (NTID) is the first and largest technological college in the world for students who are deaf or hard of hearing. As one of nine colleges within the Rochester Institute of Technology (RIT) in Rocheste ...
in the US, and the 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
Protein atonal homolog 1 is a protein that in humans is encoded by the ''ATOH1'' gene.
Function
This protein belongs to the basic helix-loop-helix (BHLH) family of transcription factors. It activates E-box dependent transcription along with TC ...
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 caused by a mutation in any one of at least 11 genes result ...
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
* Deaf hearing
* H.870
* Otologics
Otologics LLC is a medical device company that produces middle ear hearing implants. Its headquarters are located in Boulder, Colorado, with offices and a distribution network throughout Europe, Asia, and Latin America.Otologics official websitA ...
* Safe listening
Safe listening is a framework for health promotion actions to ensure that sound-related recreational activities (such as concerts, nightclubs, and listening to music, broadcasts, or podcasts) do not pose a risk to hearing.
While research shows ...
* World Hearing Day
References
External links
*
National Institute for the Prevention of Deafness and other Communication Disorders
Global Costs of unaddressed hearing loss and cost-effectiveness of interventions
World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
. 2017
Internet archive
on 12 May 2020.
Deafness and Hearing Loss
World Health Organization. 2022
Internet archive
on 9 June 2022 .
*
''U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health.'' (6 February 2018).
* Preventing Hearing Loss Caused by Chemical (Ototoxicity) and Noise Exposure Safety and Health Information Bulletin (SHIB). ''U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health''. doi:10.26616/NIOSHPUB2018124 (8 March 2018). Publication No. 2018-124.
*
''World Report on Hearing''
World Health Organization. 3 March 2021
World report
archived on 10 June 2022.
{{Authority control
Audiology
Communication disorders
Occupational safety and health
Otorhinolaryngology
Wikipedia medicine articles ready to translate
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Deafness