The effects of aging and hearing loss on distortion product otoacoustic emissions.

Abstract

We sought to demonstrate the rate of change in distortion product otoacoustic emission (DPOE) amplitude with age in relation to hearing loss in an unselected adult population. Study design and setting We conducted a cross-sectional observation study involving the Framingham Offspring Cohort. Age changes in DPOE amplitude for frequencies of f2 from 1 to 8 kHz adjusted for pure-tone threshold level were assessed by multivariate linear regression. The women showed a mean hearing threshold-adjusted loss in high-frequency DPOE amplitude of 0.6, 2.1, 2.6, and 1.1 dB/per decade at the f2 frequencies of 1, 2, 4, and 8 kHz, respectively. In contrast, the men showed no effect of age on the DPOE amplitude independent of hearing loss. Emissions were reduced or absent in the noise notch frequencies. The rate of change with age in DPOE amplitude was significantly less than the rate of change in pure-tone thresholds in both the men and the women. Women lose DPOE amplitude from both age and hearing threshold loss. Men lose more DPOE amplitude than do women, and the loss is proportional to the degree of loss of hearing threshold sensitivity. The differential effect whereby age-related hearing loss affects thresholds more than emissions suggests that strial atrophy may be a pathophysiologic factor. The use of DPOE measures for screening and monitoring cochlear status of adult women should take into account the age, pure-tone thresholds, and noise exposure status of the subjects.