Hearing Loss

Pure-tone audiometry is the standard objective test for hearing loss and test the ability to hear tones at a series of discrete frequencies, typically in the range of 250-8000 Hz at various decibel levels.

The frequencies of sound that are considered to be the most important for speech: 500, 1000, 2000, and 4000 Hz termed four-frequency pure tone average.

No universally excepted definition of hearing loss exists, guidelines define mild hearing loss generally as the inability to detect frequencies associated with speech understanding under 25dB  and moderate hearing loss as  the inability to detect those frequencies under 40 dB.

Often there is discordance between objectively measured hearing loss on pure-tone audiometry, and the subjective perceptions of hearing difficulties.

The prevalence of mild or worse speech frequency hearing loss is estimated to be about 14% among adults each 20-65 years and increases significantly with age, up to 39.3% for adults age 60-69 years.

The risk of hearing loss increases with age due to the non-regenerative nature of the hair cells in the ear responsible for hearing.

Hearing loss is associated with higher rates of disability and need for nursing care, social isolation, depression, and cognitive decline or dementia.

May increase risk of social isolation, depression, loss of autonomy, reduced employability, and neurocognitive dysfunction.

In children, without hearing rehabilitation, hearing loss can cause detrimental effects on speech, language, education, development, and cognitive outcomes.

Hearing loss is a prominent risk factor for speech and language developmental delay.

Cochlear implant‘s early in life help children attain near normal speech and language trajectories.

Despite improvements in speech and language children with hearing loss or still at risk for delay in cognitive functions such as working memory and executive functions with long-term educational and occupational consequences.

Children with hearing loss or half as likely to achieve higher education.

Hearing loss in children affects the quality of life, particularly in school and social domains, as well as behavior and behavioral disorders.

In children with hearing loss is increased behavior disorders, hyperactivity disorders, emotional, and psychiatric problems.

In children with cochlear implants there is increased risk for impaired vestibular function and ability to participate in normal childhood activities.

It is associated with pragmatic safety concerns.

Only 15-30% of eligible individuals use hearing aids.

WHO estmate 299 million men and 239 million women have hearing loss.

Common process affecting tens of millions of individuals.

Estimated 50 million Americans have hearing loss in at least 1 ear.

More than 30 million U.S. adults have hearing loss. 

 

Nearly 15% of all Americans, have some degree of hearing loss.

 

Hearing loss is most common in older adults, occurring in about one-half of adults in their 70s and 80% of those 85 years and older.

At least 1.2 million adults in the US and 50 million adults worldwide have severe or profound hearing loss, a level of impairment not sufficiently corrected with hearing aids.

The use of hearing aids is the primary intervention for newly detected mild to moderate hearing loss.

Hearing aids do not slow progression of hearing loss.

Hearing aid goals or to amplify sound reaching the middle or in the year to improve communication and function associated with hearing impairment.

Affects more than 40% of people older than 60 years, more than 60% of those older than seventy years, and nearly 80% of people older than 80 years.

Mild hearing loss in young children can impair speech and language development.

1 in 5 teenagers have hearing loss.

Approximately one In eight aged 12 years or older have bilateral hearing loss, and one in five have a unilateral hearing loss.

NHANES III conducted between 1988-1994 demonstrated 14.9% of US children aged 6-19 years had low frequency or high frequency hearing loss in at least 1 ear, and 12.5% had audiometric evidence of noise induced hearing loss.

Approximately one third of women age 50-59 years and approximately two thirds of women 60-69 years have hearing loss.

As life expectancy increases so does the prevalence of age related hearing loss.

Age related hearing loss is the most common cause of hearing loss in older adults.

Age are leading hearing loss is a type of sensorineural hearing loss related to age related degeneration and is typically gradual, progressive, and bilateral and affects higher hearing frequencies first.

This condition is underrecognized, and hearing aids and other hearing enhancement technologies are underused. 

In the US, the prevalence of hearing aid use is below 20% that of cochlea implantation is less than 5%.

Hearing loss is categorized as conductive, sensorineural, or mixed. 

 

Presbycusis is age-related sensorineural hearing loss.

 

Presbycusis is the most common type in adults. 

The prevalence of hearing loss increases with age.

Approximately 2/3 of people 70 years of age or older in the US have hearing loss.

Advanced age, recreational or occupational noise exposure, hereditary factors, and exposure to ototoxic medications collectively are the most common causes of sensors- neural hearing loss that develops in adulthood.

Many conditions lead to the development of sensori-neural hearing loss, and most have a common pathway whereby damaged or missing sensory hair cells in the cochlea no longer transduce acoustic energy into neural action potentials that are processed by the CNS and perceived as understandable speech.

Cochlear hair loss is presently irreversible.

Presently, there are no approved pharmacological surgical treatments that reverse sensorineural hearing loss and reinstate normal acoustic hearing.

Clinical management of hearing loss revolves around prevention and rehabilitation through the use of hearing aids or cochlear implants.

Hypertension is independently associated with a higher risk of hearing loss in women.

Unilaterally hearing loss in children is most commonly (30%) associated with craniofacial anomalies, family history of hearing loss, and syndromes associated with hearing loss.

Often unrecognized by patients and underdiagnosed by physicians and markedly undertreated.

Consequences include social isolation, functional decline, poor quality of life, depression, and cognitive defects.

Severity of hearing loss based on volume at which pure tones can be heard on audiometry.

In children and adolescents some hearing loss may be related to infection, genetic syndromes, complications of prematurity, perinatal complications, exposure to ototoxic medications, head trauma and noise exposure.

Prevalence of hearing loss among US adolescents age 12-19 years was greater in 2005-2006 compared to 1988-1994 (Shargorodsky J, NHANES 2005-2006).

Hearing screenings in infancy, the efficacy of hearing aids and cochlear implant, the proliferation of genetic studies expanding understand of genes involved in hearing, knowledge about the interaction between hearing and cognition have improved the understanding about children with hearing loss.

Today more than 75% of children with hearing loss can attend public schools main stream with normal hearing students.

Normal hearing defined by the American Speech-Language-Hearing Association as a hearing threshold of 0-25 dB, with thresholds for mild, moderately severe, severe, severe and profound hearing loss are 26-40 dB, 41-55 dB, 50-70, 71-90 dB and 91 dB or greater, respectively.

Smoking is associated with damage to the outer hair cells of the cochlea, increased oxidative stress due  to degeneration of reactive oxygen species and elevated systemic inflammatory markers and is associated with the quired hearing loss.

The magnitude of hearing loss is larger with greater number of pack years smoked.

Discontinuing smoking is associated towards diminished risk of hearing loss.

Sensorineural hearing loss is caused by lesions in the cochlea, VIIIth cranial nerve, or the CNS.

Common causes of sensineural hearing loss include age-related hearing loss, noise exposure, ototoxic, viral or bacterial infections, autoimmune diseases, temporal bone trauma, VIIIth cranial nerve tumors, and congenital hearing loss.

Hearing loss is the predominant otologic manifestation in primary and secondary malignancies of the temporal bone, tinnitus, disequilibrium, and vertigo, may also be present with either type of lesion.

Acoustic neuroma is it benign lesion that arises from the vestibulocochlear nerve, cranial nerve VIII, and may be located in the internal auditory canal, cerebellopontine angle, or both sites simultaneously.

Malignant lesions may metastasize to the temporal bone and result in hearing loss.

With sudden hearing loss underlying malignancy must be considered if there is pain, dizziness, facial nerve paralysis with chronic ear discharge.

Carcinoma of the breast is the most common malignancy to metastasized to the temporal bone.

Hearing loss has been associated with depression, dementia, cognitive decline, poor physical functioning, and falls.

It is estimated that up to 35% of dementia cases potentially preventable hearing loss is considered the largest modifiable risk factor.

Conductive hearing loss vaused by mechanical imparment in transmission of sound from the externl to the internl ear.

Conductibe hearing loss caused in adults by cerumen impaction, otitis media and otosclerosis.

Inner ear and can arise from the external ear canal, the tympanic membrane or the middle ear.

Causes of conductive hearing loss include: impacted cerumen in the external canal, perforation of the tympanic membrane, otitis media, otosclerosis, ossicular discontinuity and the presence of a cholesteatoma.

Age-realted hearing loss is known as presbycusis.

Age related hearing loss is the most common type of hearing loss in older individuals.

Age related hearing loss, as noted above, is a multifactorial sensorineural loss affecting high frequencies initially.

Age related hearing loss progresses over decades in adults over the age of 50 years.

Presbycusis strongly associated with age and noise exposure.

Hearing loss, especially in older adults, is associated with the inability to effectively communicate, which can lead to social isolation.

Frequent component of age related hearing loss is a central auditory processing disorder, which further impars speech discrimination.

Patients with even mild hearing loss are twice as likely to develop dementia and risk increases with the severity of hearing loss.

The risk of dementia doubles with mild hearing, triples with moderate hearing loss and is five times higher for severe hearing loss (Lin FR).

Central auditory processing disorder is common in the elderly with a prevalence of 95% in individuals 80 yers and older (Stach BA et al).

The National Health and Nutrition Examination Survey 2005-2006 found that among adults aged 70 years, the prevalence of hearing loss was 63%, and moderate to severe hearing loss was noted in 27%.

Hearing loss increases geometrically with age (Dillon CF et al).

Framingham Study the frequency of patricipants 65-69 years and 85-90 years who reported hearing problems was 34% and 72%, respectively (Gates GA et al).

Age related hearing loss is a multifactorial sensorineural loss that includes an impaired speech discrimination component.

Major treatment for age-related hearing loss is amplification.

Hearing aids improve hearing function and hearing related quality of life.

Conduction hearing loss can be treated by restoring the sound conduction pathway by repairing tympanic membrane abnormalities, ossicular reconstruction or removal of a cholesteatoma or the use of hearing aids.

In a study of 3000 adults age 21-84 years revealed 14.1% had impaired hearing, and the incidence increased to 42.7% in those aged 65 to 84 years (Nash SD et al).

Up to one-third of adults over the age of 65 years report hearing loss in one ear.

Hearing loss is prevalent in almost 2/3 of adults older than 70 years of age and is an undertreated process.

Hearing loss is independently associated with accelerated cognitive decline in community dwelling older adults.

Individuals having hearing loss demonstrate a 30-40% accelerated rate of cognitive decline, and a 24% increased risk for incident cognitive impairment during a six-year follow- up up comparaed to individuals having normal hearing (Lin FR et al).

Estimated 26.7 million adults in the US have clinically significant hearing loss, but fewer than 15% use hearing aids(Chen et al).

Among individuals with mild hearing loss hearing aid use is low at about 2-3%, with usage generally increasing for older age groups in those with moderate or severe hearing loss

Estimated that 30 million or 12.7% of individuals 12 years and older have bilateral hearing loss, and an estimated 48.1 million or 20.3% when one includes individuals with unilateral hearing loss (Lin FR et al).

Age related hearing loss independently associated with poorer cognitive functioning, incident dementia compared with normal hearing individuals.

Hearing loss affects the ability of older people to remain productive and independent.

Patients with mild, moderate and severe hearing loss have a 2,3, and 5 fold increased risk of developing dementia, respectively.

1 in 1000 children are born with significant sensorineural hearing loss and another 1 in 1000 will have such a hearing loss by age 9.

There are hundreds of gene mutations that can cause sensorineural hearing loss as a sole clinical abnormality or part of a syndrome of other abnormalities.

Patients with suspected hearing loss should undergo hearing tests such as the whispered voice test or audiometry. 

 

Patients should then undergo examination for cerumen impaction, exostoses, and other abnormalities of the external canal and tympanic membrane, in addition to a neurologic examination. 

Individuals who present with sudden hearing loss requires an urgent evaluation as rapid diagnosis and treatment increase the possibility of recovery of hearing and lead to early identification of potentially treatable pathology.

Sudden sensorineural hearing loss is defined as a decrease in hearing of 30 dB or greater across at least 3 consecutive frequencies over a period of three days or less.

Etiology of sudden sensorineural hearing loss is elusive in up to 90% of cases.

Ten cent of cases of sudden sensorineural hearing loss associated with neoplatic, autoimmune, infectious, circulatory, coagulation, and demyelating disorders.

Sudden sensorineural hearing loss of 30 dB or more within 72 hours,requires prompt otolaryngology referral. 

 

Computed tomography or magnetic resonance imaging is indicated in patients with asymmetrical hearing loss or sudden sensorineural hearing loss, and when ossicular chain damage is suspected. 

Individuals with hearing loss have lower cardiorespiratory fitness is an indication of physical activity levels.

May be associated with furosemide, most commonly when used intravenously.

Hearing loss associated with furosemide is usually reversible.

Delaying treatment for hearing impairment may make it more difficult, if not impossible, to gain back the level of hearing close to the previous level due to the loss in the brain’s auditory processing capabilities.

Treating cerumen impaction with irrigation or curettage is potentially curative. 

 

Treatment may include auditory rehabilitation, education, and eliminating or reducing use of ototoxic medications. 

 

Patients with sensorineural hearing loss should be referred for consideration of hearing aids. 

 

Cochlear implants can be helpful for those with refractory or severe hearing loss.

 

Only about one-third of people with self-reported hearing loss have ever had their hearing tested.

 

About 15% of people eligible for hearing aids consistently use them.

Hearing aids provide sufficient benefit for most patients who have relatively good speech recognition and less than severe to profound hearing loss at low frequencies to and less than 90 dB high hearing  level at high frequencies.

For patient with poor speech recognition and more advanced bilateral sensorineural hearing loss, cochlear implantation provides the only effective means of auditory rehabilitation.

Among older adults with hearing loss, a community delivered intervention that included a personal sound amplification device, compared with wait-list control, significantly improved self perceive communication function at three months.