Age Effects on Cochlear Reflectance in Adults.

Objectives: Cochlear reflectance (CR) is the cochlear contribution to ear-canal reflectance. CR is a type of otoacoustic emission that is calculated as a transfer function between forward pressure and reflected pressure. The purpose of this study was to assess effects of age on CR in adults and interactions among age, sex, and hearing loss. Design: Data were collected from 60 adults selected for their age (e.g., 20-29, 30-39, 40-49, 50-59, 60-69, 70-79 years) and normal middle ear status. A wideband noise stimulus presented at three stimulus levels (30, 40, 50 dB SPL) was used to elicit CR. Half-octave bands of CR signal magnitude (CRM), CR noise, and the CR signal-to-noise ratio (CR-SNR) were extracted from the wideband CR response. Regression analyses were conducted to assess interactions among CR, age, sex, and pure-tone thresholds at closely matched frequency bands across stimulus levels. Results: Although increased age was generally associated with lower CRM and CR-SNR at some band frequencies and stimulus levels, no significant effects of age remained after controlling for effects of pure-tone thresholds. Increases in pure-tone thresholds were associated with lower CRM and CR-SNR at most frequency bands and stimulus levels. Effects of hearing sensitivity were significant at some frequencies and levels after controlling for age and sex. Conclusions: When effects of age were controlled, adults with better hearing had significantly larger CRM and CR-SNR than those with poorer hearing. In contrast, when effects of hearing were controlled, no significant effects of age on CRM and CR-SNR remained.