Hearing Impairment
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Research suggests that early poor hearing can affect [3]:
- Speech and language development
- Cognitive development and auditory processing skills
- Social/emotional wellbeing
- School attendance
- Employment options
People with hearing impairment may be concerned with [1]:
- Difficulty hearing and understanding other people
- Hearing the television, or speech in noisy environments
- Missing fire alarms, phone calls
- Limitations of hearing aids and interpreters
- Stigma
- Distress or fatigue with the communication process.
In babies and children, the following might be observed [4]:
- Not startling at loud noises, or not locating sound by age 6 months
- Delayed or unclear speech
- Other delayed milestones
- Listening to television on high volume
The following steps are needed for effective hearing [1]:
- Sound waves travel down the ear canal to the eardrum causing it to vibrate.
- These vibrations pass to three small bones (ossicles) and are transmitted across the middle ear.
- The vibrations move into the fluid of the cochlea in the inner ear and cause tiny rippling waves.
- Hair cells on the cochlea’s elastic membrane are moved by the rippling fluid, opening microscopic channels.
- Chemicals flow through the channels into the hair cells and cause the release of a neurotransmitter which results in an electrical signal being generated.
- The auditory (hearing) nerve transmits the electrical signal to the brain for processing in a complex series of relay stations, which results in hearing.
Hearing impairment can be classed as:
- Conductive (conduction of sound) caused by conditions such as ear wax, abnormal ear development, outer or middle ear (otitis media) infection, trauma, growths, or immobile middle ear bones
- Sensorineural (inner ear and/or auditory nerve problems) caused by genetic or environmental conditions such as severe newborn jaundice, viruses such as bacterial meningitis, medications and noise exposure
- Mixed (both types).
- Auditory neuropathy: A form of hearing impairment involving disorganisation of nerve firing patterns in the pathways between the inner ear and the brain
Common causes are listed in Table 1.
TABLE 1
Common causes for hearing impairment [3-10]
| Common causes | Explanation | |
|---|---|---|
Babies |
Genes (50% of cases) |
May be a family history of hearing loss About 30% of genetic causes are related to a syndrome (where other complex medical issues are present, such as Usher Syndrome). Mutations in the genes needed to produce the proteins called Connexin 26 and Connexin 30 are the most common genetic causes of hearing impairment that are not syndromic. |
|
Infection (25%) Head trauma |
About 25% of cases are due to infections during pregnancy (such as cytomegalovirus), or postnatal complications |
|
|
Unknown (25%) |
25% of cases have no known cause |
|
Children |
See causes (babies) |
|
|
Otitis media |
This is the most common cause of hearing impairment in children and is usually temporary when treated appropriately. 80% of children have at least one episode of otitis media by the age of three. 40% of children will have over five episodes by the age of seven. Fluid in the middle ear persisting beyond 6–12 weeks is called glue ear and is usually treated surgically with grommets |
|
|
Environment |
High blood lead levels are linked to sensorineural hearing impairment. Household overcrowding, inadequate access to running water, sewerage and waste removal increase risk of hearing impairment. |
|
|
Healthcare access |
Living in remote areas limits healthcare access, causing delayed diagnosis of middle ear disease |
|
Adults |
See causes (babies, children) |
|
|
Presbycusis (age-related hearing loss) About 30% of people aged 65-74, and about 50% of people over 75 |
Affects hearing in both ears, typically from age 60 Thought to be due to factors including:
|
|
|
Noise exposure |
This is the most common preventable cause of hearing loss and is due to damage to the hair cells of the inner ear. Can be from intense sound (such as gunshots/explosions), or ongoing exposure to high level noise over a prolonged period. |
|
|
Other diseases (not all listed) |
Eustachian tube dysfunction Otosclerosis Meniere’s disease Head injury, stroke |
In Australia, newborn babies can have a free screening test, usually within the first few days of birth.
Babies who do not pass will go on to have further diagnostic tests with an audiologist to determine their hearing ability.
Other tests that children and adults with hearing impairment may require are included in Table 2.
TABLE 2
Main hearing tests for children and adults
| Pure-tone audiometry |
|
|---|---|
| Speech testing |
|
| Tympanometry |
|
A range of audiological tests and physical examination is needed for a full diagnosis of hearing impairment.
The degrees of hearing impairment can be categorised as [11]:
- Mild (21–45dB)—difficulty hearing soft sounds or speech in conversation
- Moderate (46–60dB)—hard to hear conversational speech, especially if background noise present
- Moderately severe (61–75dB)—very difficult to hear ordinary conversation
- Severe (76–90dB)—cannot hear conversational speech
- Profound (91dB)—almost all sounds are inaudible.
Management options, useful tools and ways of coping with hearing impairment are listed in Table 3.
TABLE 3
Treatments and tools for hearing impairment [10,12,13]
| Management options and tools for managing hearing impairment | Description |
|---|---|
|
Hearing aid |
Electronic device which amplifies sound so it can be heard |
|
Cochlear implant |
Electronic device inserted into the inner ear with an external processor worn behind the ear that encodes the external sound into electrical impulses in the inner ear to activate the auditory (hearing) nerve |
|
Assistive listening devices |
Phone amplifying devices, mobile device apps, closed captions, hearing-loop (induction loop) systems, alerting devices |
|
Lip reading and sign language |
Training can help people learn these skills |
|
Reducing barriers when talking |
Converse with minimal background noise Get the person’s attention before speaking Ensure good lighting, face the person, ensure speaker’s mouth is visible Speak more slowly than usual but naturally |
Childhood immunisation protects against some bacteria that cause otitis media.
Ear infection can be treated by antibiotics [3], and grommets can be used in some cases of glue ear.
Education on prevention is important, from childhood intervention programs through to regulations around workplace exposure, particularly in mining, wood product manufacture and building construction.
Avoiding excessive noise sources, and using personal hearing protection such as earmuffs and ear plugs, where appropriate, is recommended [8].
New tests and management options under development at the Bionics Institute
Deep expertise in hearing research at the Bionics Institute has given rise to ground-breaking tests and new management options:
• Research to develop ways to individually optimise the benefits gained from cochlear implants
• A new infant hearing test that images the brain using near-infrared light to give children with hearing impairment the best chance to hear and speak.
• A world-first test for tinnitus that can diagnose presence and severity of tinnitus with high accuracy
• Research into the genetic modification of nerve cells to respond to light and electricity to combat the issue of current spread in cochlear implants
• Development of therapeutics using nanotechnology to restore age-related hearing impairment.
With your help, we can accelerate the evolution of this research, improving the lives of people with hearing impairment.
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Medical Disclaimer
This article contains general information relating to a medical condition. Such information is provided for informational purposes only and does not replace medical advice given by your healthcare professional.
References
1. Vas V, Akeroyd MA, Hall DA. A Data-Driven Synthesis of Research Evidence for Domains of Hearing Loss, as Reported by Adults With Hearing Loss and Their Communication Partners. (CC BY 4.0). Trends Hear [Internet]. 2017 [cited 2022 May 7];21:1–25. Available from: https://us.sagepub.com/en-us/nam/open-access-at-sage
2. Australian Institute of Health and Welfare. 3.15 Vision and hearing disorders (Australia’s health 2016). (CC BY 4.0) [Internet]. 2016 [cited 2022 May 5]. Available from: https://www.aihw.gov.au/getmedia/48ee92a8-d373-4354-8df2-d664a974034f/ah16-3-15-vision-hearing-disorders.pdf.aspxn/
3. 6.4 Ear health and hearing loss among Indigenous children. (CC BY 4.0) [Internet]. Australian Institute of Health and Welfare. 2018 [cited 2022 May 5]. Available from: https://www.aihw.gov.au/getmedia/12c11184-0c0a-43ad-8386-975c42c38105/aihw-aus-221-chapter-6-4.pdf.aspx
4. What is Hearing Loss in Children? [Internet]. Source: CDC [Public domain]. 2021 [cited 2022 May 7]. Available from: https://www.cdc.gov/ncbddd/hearingloss/facts.html
5. Cheslock M, Jesus O De. Presbycusis. (CC BY 4.0). StatPearls [Internet] [Internet]. 2021 Nov 14 [cited 2022 May 7]; Available from: https://www.ncbi.nlm.nih.gov/books/NBK559220/
6. Noise-Induced Hearing Loss (NIHL) [Internet]. Source: NIDCD. 2022 [cited 2022 May 8]. Available from: https://www.nidcd.nih.gov/health/noise-induced-hearing-loss
7. Le TN, Straatman L V., Lea J, Westerberg B. Current insights in noise-induced hearing loss: a literature review of the underlying mechanism, pathophysiology, asymmetry, and management options. (CC0 1.0). J Otolaryngol – Head Neck Surg 2017 461 [Internet]. 2017 May 23 [cited 2022 May 10];46(41):1–15. Available from: https://journalotohns.biomedcentral.com/articles/10.1186/s40463-017-0219-x
8. Vasconcellos AP, Colello S, Kyle ME, Shin JJ. Societal-level risk factors associated with pediatric hearing loss: A systematic review [Internet]. Vol. 151, Otolaryngology – Head and Neck Surgery (United States). 2014. p. 29–41. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478237/#!po=73.8095
9. Monasta L, Ronfani L, Marchetti F, Montico M, Brumatti LV, Bavcar A, et al. Burden of Disease Caused by Otitis Media: Systematic Review and Global Estimates. (CC BY). PLoS One [Internet]. 2012 [cited 2022 May 31];7(4):1–12. Available from: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0036226&type=printable
10. Age-Related Hearing Loss [Internet]. Source: NIDCD. 2022 [cited 2022 May 5]. Available from: https://www.nidcd.nih.gov/health/age-related-hearing-loss#2
11. Hearing checks and hearing aids. (CC BY 4.0) [Internet]. The State of Queensland 1995–2022. 2019 [cited 2022 May 8]. Available from: https://www.qld.gov.au/health/services/oral-eye-ear/hearing
12. Hearing Loss: A Common Problem for Older Adults [Internet]. Source: National Institute on Aging. 2018 [cited 2022 May 5]. Available from: https://www.nia.nih.gov/health/hearing-loss-common-problem-older-adults
13. Cochlear Implants [Internet]. Source: NIDCD. 2021 [cited 2022 May 10]. Available from: https://www.nidcd.nih.gov/health/cochlear-implants
