The effects of aging on otoacoustic emissions.

Otoacoustic emissions were measured in 42 normal hearing subjects ranging from 20 to 80 years old. For each subject spontaneous, click-evoked, tone-burst-evoked, stimulus frequency and distortion product emissions were measured across a wide intensity range for frequencies between 1 and 3 kHz. Although there are significant differences between age groups, the results indicate no age effect independent of hearing sensitivity on any type or parameter of otoacoustic emissions (OAE). The effect of increasing age is confounded with the effect of decreasing sensitivity such that post hoc analyses are inadequate to separate the effects of sensitivity and age on otoacoustic emissions. Even within the range of audiometrically normal hearing, OAE characteristics vary with threshold for all age groups. The conclusion is that hearing sensitivity must be included as a controlled variable in order to accurately assess intrinsic aging effects.