This group of six projects will investigate otologic, epidemiologic, audiologic, neurophysiologic, morphologic, histochemical, and laryngologic aspects of age-related communication disorders, chiefly clinical presbycusis (hearing dysfunction in the elderly), and presbylaryngis (laryngeal dysfunction in old age). From this information we hope to better understand the pathophysiology of these disorders, develop a new diagnostic test, establish better-defined hypotheses for future studies and, thus, add to our ability to prevent, modify, and, eventually, treat age-related communication dysfunction. The first two projects examine the epidemiology of clinical presbycusis and its possible relationship to cardiovascular disease by analyzing the extensive HANES I data base (project one) and by studying the auditory function of the Framingham cohort (project two). Project three will examine the validity and reliability of cochlear distortion-products as an objective test of cochlear dysfunction using noise-damaged cats and presbycusic baboons and humans. Project four will study the electrophysiologic and morphologic changes in elderly baboons with auditory dysfunction (identified by electrocochleography and auditory brain-stem responses) compared to young and aged controls. Project five will study the nerve conduction time, stimulus parameters, and strength of the glottic closure relflex as well as muscle tension properties and morphology in young and aged baboons in order to isolate the pathophysiologic changes responsible for aspiration in the elderly. Project six will examine changes in steroid receptors in brain and larynx as a function of age and sex in the baboon.
