Effects of age and interstimulus interval on the brainstem auditory evoked potential.

Brainstem auditory evoked potentials (BAEPs) were studied in young (mean age 25 years; n = 8) and very healthy elderly women (mean age 71.2 years; n = 8) in order to evaluate the effects of age on transmission time over the brainstem auditory afferent pathway. Peak latencies, interwave latencies (ILs) and response amplitudes were determined at interstimulus intervals (ISIs) of 100, 50, 20 and 10 msec. Four repeated measures were obtained at each ISI in order to assess response variability as a function of age. While the elderly group had delayed peak latencies for all BAEP components, ILs were equivalent in the two age groups. Response amplitude tended to be reduced in the elderly compared to the young group and this effect was dependent upon ISI. Latency values (both peak and ILs) increased with decreasing ISI but there was no age-ISI interaction. Response variability did not change with age. The peak latency increases observed in the elderly were shown to be due to peripheral processes (mild presbycusis). The lack of an age effect for ILs and the lack of an ISI-age interaction indicate no age related slowing of central transmission time in the afferent auditory system at least to the region of the superior olivary complex and inferior colliculi.