Effects of noise exposure and hypercholesterolemia on auditory function in the New Zealand white rabbit.

Abstract

An association between hypercholesterolemia and high-frequency hearing loss has been suggested previously. Most data have been epidemiologic, and only recently have experimental studies appeared supporting this observed association. It is unclear whether this hearing loss is related solely to hypercholesterolemia or if it is a consequence of cholesterol-induced vascular changes. The New Zealand White rabbit was used to study the auditory effects of noise, hypercholesterolemia, and the combination of both. Auditory function was evaluated with far-field monitoring of click-evoked auditory brain stem responses by comparing latency/intensity functions and absolute click-evoked thresholds. Hypercholesterolemia was maintained for only 3 weeks, theoretically eliminating atherosclerotic vascular changes as a mechanism contributing to observed changes. Auditory function was unchanged after 3 weeks of hypercholesterolemia. Also, the changes observed after noise exposure were comparable between the normal and the hypercholesterolemic groups. We conclude that if hypercholesterolemia contributes to high-frequency hearing loss, the pathophysiology is related to cholesterol-induced vascular changes, not solely to hypercholesterolemia.