The effects of aging on evoked otoacoustic emissions and efferent suppression of transient evoked otoacoustic emissions.

OBJECTIVE There is still controversy regarding the effects of aging on evoked otoacoustic emissions (EOAEs), as well as on the efferent system measured by contralateral acoustic stimulation of EOAEs. The purpose of this study was to investigate the deterioration in EOAEs and efferent suppression (ES) in a representative sample statistically controlling for the differences in hearing thresholds. METHODS Seventy-one ears (20-79years) were included in the study, 47 of which had normal hearing thresholds, and 24 ears had a sensorineural high-frequency hearing loss caused by presbycusis. The effects of aging on transient evoked (TEOAEs) and distortion product OAEs (DPOAEs), and on ES were evaluated using multiple regression and correlation coefficients. RESULTS EOAEs and ES were more strongly correlated with age, than with pure-tone thresholds (PTTs). Moreover, the increase in the amount of variance explained by the regression model using both predictors was larger for PTTs as compared to the variable age. CONCLUSIONS The deterioration of EOAEs and ES with advancing age is caused mainly by pure age-effects, and additionally by the reduction in hearing thresholds. SIGNIFICANCE The relative contribution of age and hearing thresholds on EOAEs, as well as on ES is important for their interpretation in clinical settings.