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- High-frequency hearing loss.
- Reduced clarity of hearing.
- Absence of retrocochlear pathology.
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- Generalized imbalance.
- Absence of vertigo.
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According to the World Health Organization, the proportion of population that are elderly is increasing at a rapid rate—by 2025, nearly 1.2 billion people will be over the age of 60! Consequently, the prevalence of age-related auditory and vestibular dysfunction will increase. Genetically determined and environmentally affected, the inner ear, like other organ systems, undergoes degenerative changes with aging. These changes result in a variable functional disability. In the United States, hearing difficulty is reported by 25–30% of people in the age group of 65–70 years and by nearly 50% of those over 75 years of age. It has been estimated that between 1.5% and 3.0% of the total population would benefit from hearing aids. Vestibular dysfunction is also common in the elderly, with reported prevalence of vertigo, dysequilibrium, or imbalance to be as high as 47% in men and 61% in women over the age of 70. The incidence of falling in individuals over the age of 65 is between 20% and 40% in those living at home and is twice as frequent for the institutionalized elderly. These falls are associated with significant morbidity and mortality and constitute one of the leading causes of death among the elderly.
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The specialized neural cells of the auditory and vestibular systems are nonmitotic and thus cannot undergo replication and renewal. During the course of a lifetime, DNA transcription errors and insoluble pigments accumulate, and protein synthesis becomes increasingly inefficient. In addition, environmental and external factors such as noise trauma, physical trauma, ototoxic substances, and medications contribute to senescence. More recently, the contribution of genetics to age-related hearing loss is being appreciated.
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Age-Related Hearing Loss
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Hearing loss in the elderly is multifactorial and is due to the convergence of various risk factors. Presbycusis is the otherwise unexplained, slowly progressive, predominantly high-frequency symmetric hearing loss due to the aging process (Figure 53–1). Progressive high-frequency hearing loss has been clearly documented by numerous studies in populations over the age of 40 (Figure 53–2A). Older patients with presbycusis also have more diminished speech discrimination than younger patients with the same level of pure-tone averages (Figure 53–2B). This suggests that neural processing is affected in addition to end-organ dysfunction.
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