Timothy J. Lewis

Outline

Prevalence and impact

Hearing loss is common in older adults and has serious psychosocial and functional consequences. It affects one third of individuals 65 years or older and ranks as the third most common chronic disease in that age category. Hearing impairment rises geometrically with age from 16% at age 60, 32% at age 70, and 64% at age 80. The prevalence of hearing disability also rises with age (Figure 25-1). Functional deficits associated with hearing loss include diminished ability to recognize speech amid background noise and to locate and identify sounds that may have an important warning or alarm significance. The communication difficulties experienced by the hearing impaired also affect other people in their environment such as family members and coworkers. Hearing loss is associated with depression, social isolation, and poor self-esteem, as well as cognitive decline.

Despite the importance of hearing function in everyday life, hearing loss is often a poorly recognized and undertreated problem. The insidious onset and progression of age-related hearing loss (ARHL) likely contributes to its under-recognition. Although 26.7 million U.S. adults aged 50 years or older have clinically significant hearing loss, fewer than 15% use hearing aids.¹ In the United States, only about 40% of people with moderate to severe ARHL own hearing aids; that percentage drops to 10% among persons with mild ARHL.²

Barriers to the evaluation and treatment of hearing loss

The subtle presentation of ARHL is rarely a call to action for either the afflicted person or his or her doctor. In the mild to moderate stages, ARHL is often characterized by the inability to understand words rather than the inability to hear, and the common refrain of “My hearing is fine. You’re just mumbling.” The functional consequences of hearing disability, however, should not be underestimated. When affected individuals do become aware of their hearing loss, initially they may try to compensate and conceal it, but symptoms eventually give their secret away. Persons wait on average 7 to 10 years between signs of hearing loss and audiologic consultation.³ Affected persons may not be aware of the functional deficits or know what they are missing. Older persons who have ARHL but do not pursue hearing aids demonstrate less problem awareness on questionnaires of self-perceived hearing disability and have a greater tendency to deny communication problems. The high cost of hearing aids is an additional barrier to treatment for many older Americans.

Primary care providers can help with recognition and treatment of adults with hearing disability by routinely asking about hearing problems and watching for signs or symptoms of hearing disability, such as communication difficulties, social withdrawal, or depressed mood. When the history and examination suggest ARHL, timely referral to an audiologist can help improve the outlook for persons with hearing disability.

Aging changes

Usual aging changes in the auditory system contribute to diminished hearing performance among older adults (Box 25-1). Prior noise exposure, middle ear disease, and vascular disease affect the progression of ARHL. Longitudinal studies demonstrate that hearing declines gradually in 97% of the population as evidenced by diminished pure-tone threshold sensitivities with age. Individuals under 55 years of age typically lose hearing at a rate of 3 dB per decade, and those over 55 years at a rate of 9 dB per decade.⁴ The ability to understand speech in a backdrop of competing conversations begins to deteriorate slowly in the fourth decade of life, and accelerates after the seventh decade. As adults age, it also becomes increasingly difficult for them to understand speech that is rapid, poorly transmitted, or mispronounced.

Risk factors and pathophysiology

The two major forms of hearing loss are sensorineural and conductive disorders; each has its own risk factors and causes. Disorders of the inner ear cause sensorineural hearing loss by damaging the cochlea, eighth cranial nerve, or internal auditory canal. Presbycusis is a distinct age-related sensorineural hearing loss that is the most common cause of ARHL. The hallmark of presbycusis is bilateral, symmetric, high-frequency sensorineural hearing loss. Advancing age is the predominant risk factor. The cochlea appears to be the primary site of pathogenesis, although the precise cause of presbycusis remains uncertain.

Noise-induced hearing loss (NIHL) is the second most common cause of sensorineural hearing loss among older adults. The pathogenesis of NIHL involves direct mechanical injury to the sensory hair cells of the cochlea. Continuous noise exposure poses greater risk than intermittent exposure.

Disorders of the external ear or the middle ear can cause conductive hearing loss by interfering with the mechanical transmission of sound in the inner ear. Conductive disorders typically have a mechanical cause. And occlusion of the external ear canal by cerumen is the most common cause of conductive loss. Other risk factors for conductive loss include perforated ear drum, fluid in the middle ear, and disarticulation of the ossicular chain. Specific disease entities causing conductive hearing loss are described in the following section.

Differential diagnosis and assessment

Hearing loss can result from diseases of the auricle, external auditory canal, middle ear, inner ear, or central auditory pathways. Diseases of the inner ear or eighth nerve cause sensorineural hearing loss, whereas diseases of the auricle, external auditory canal, or middle ear generally cause conductive hearing loss. Mixed loss refers to a combination of conductive and sensorineural loss. Central auditory processing dysfunction is a major factor affecting speech perception in the seventh decade and beyond. Attention should be paid to memory function also because memory impairment affects central auditory ability.⁵ Box 25-2 lists the differential diagnosis.

Detection and evaluation of hearing loss

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