PRESBYCUSIS--BIOMEDICAL RISK FACTORS

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Presbycusis is a common problem that is increasing in prevalence as the number of elderly persons in our society increases. The prevalence and severity of presbycusis vary substantially in different populations but the sources of this variability have not been delineated. The proposed research will examine the epidemiology of presbycusis in relation to biomedical risk factors with the goal of determining the relative contributions of agerelated degeneration and age-related diseases to: a) presbycusis in general; b) the major sites of dysfunction, i.e. cochlear, retrocochlear, and central; and c) the specific types of presbycusis, i.e. sensory, neural, strial, and conductive. The proposed research will obtain comprehensive measures of peripheral and central auditory function in an elderly cohort that has been surveyed for cardiovascular disease for over 40 years. This will be the third audiometric assessment of the Framingham cohort, which will permit a) the first 15 year longitudinal analysis of the incidence of hearing loss in elderly men and women, b) the first longitudinal assessment of the incidence of central auditory dysfunction, and c) the opportunity to compare the incidence of hearing loss in relation to the incidence of systemic disorders, including cardiovascular disease and its antecedent risk factors. Testing the offspring of the cohort using the same protocol will establish a baseline for future longitudinal testing and lay the groundwork for future genetic studies by documenting those with: a) exogenous causes of hearing loss prior to the onset of significant age effects and b) possible genetic protection from presbycusis. Tests include pure-tone thresholds, immittance audiometry, distortion-product otoacoustic emissions, speech discrimination in quiet and a battery of central auditory tests. Comparing these tests with those obtained 9 and 15 years earlier may reveal patterns of change not evident in cross-sectional studies. Multiple measures of hearing function should improve our ability to identify each type of presbycusis and better define the prevalence of each. Gender-related factors will be studied to explain the more rapid low-frequency loss in women. By comparing changes in audition with changes in biomedical status, including cardiovascular disorders, we will test the hypothesis that presbycusis and systemic vascular disease share common risk factors. Knowing whether cardiovascular disease or its precursors are co-factors in the pathogenesis of certain types of presbycusis will allow a rational approach to prevention and possible treatment.