Ear Diseases

Prevalence

The definition of hearing impairment varies within the otolaryngology community. Some sources consider an elevation of 20 decibels above the hearing threshold to define hearing loss, whereas others use 26 decibels as the criterion. The current average is 25 decibels above the hearing threshold in the poorer ear. For noninstitutionalized elderly, the prevalence of hearing impairment varies from 30% to 83%. In 1986, the National Center for Health Statistics stated that hearing impairment was the fourth most prevalent condition in the elderly. In 2003, it was the most prevalent chronic condition among males over 65 years of age and was the third most prevalent condition for males and females combined. Current estimates of hearing impairment among the geriatric cohort are 56% of persons 65 to 69 years of age and 89% of persons older than 85 years of age.

In 2003, of 28 million hearing-impaired individuals, 75% were over 55 years of age. It is well accepted that men experience a higher rate of hearing impairment than do women, especially in higher frequencies. In 1990, George Gates and colleagues described three factors in addition to genetic predisposition associated with presbycusis (age-related hearing loss): (1) intrinsic damage and age-related degeneration, (2) lifetime occupational and recreational noise exposure, and (3) chronic diseases, ototoxic medications, and diet. With age, the accumulation of these factors is likely to result in progressive hearing loss.

Age-Related Changes

The outer ear includes the pinna and external canal. Earlobes and creases grow with age. The pinna and external meatus lose elasticity and muscle tonicity, leading to thinning and fragility. The pinna is often a site for squamous and basal cell carcinomas. In fact, 90% of squamous cell carcinomas in older adults occur on the face or ears. Cerumen production decreases from diminished gland activity.

The middle ear is a mediator to the inner ear. It extends from the tympanic membrane to the cochlea, including the epitympanic recess and bony structures [Page 174]such as the stapes, malleus, and incus. It linearly transmits signals up to 130 decibels to the cochlea and raises the pressure by 25 to 30 decibels to amplify sound for adequate interpretation by the cochlea. With age, the tympanic membrane stiffens and the tensor tympani and stapedius muscles lose their elasticity. Arthritis appears to result in degeneration of the incudomalleal and incudostapedial ossicle joints. Despite these middle-ear changes, audiologic studies have shown minimal effect on hearing. The middle ear's amplification and transmittal functions appear not to be affected by age.

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