CAEP are not only a useful tool for objective measurement of hearing thresholds for
complex stimuli, but they also allow gaining information on the integrity of the
thalamo-cortical auditory pathway. As a part of the aging process, morphological and
functional changes of the cochlea, the auditory nerve and the central auditory
pathway will lead to the development of a slowly progressive hearing loss. To
evaluate such changes, the latencies and morphology of the CAEP after different
syllable and noise stimuli were investigated in normal-hearing young adults and
adults older than 50 years.
61 adults were examined; 41 with age average of 28 2/12 years and 20 with age
average of 55 6/12 years. Normal hearing was confirmed by measurement of
otoacoustic emissions. CAEP were recorded with three speech stimuli Ba (600 Hz), Ga
(2000 Hz), Sa (6500 Hz) and three in frequency matched narrowband noises (low:
70-1000 Hz, mid: 1-3 kHz, high: 3-6 kHz) presented by loudspeakers at 60dB SPL. CAEP
showed an excellent identifiability (94-100%) for all stimuli. Changing the
stimulus did not result in statistically significant differences in latency within
a
group. The mean Latency of P2 was observed to increases with increasing age. The
Mann-Whitney U test showed a statistically significant difference in P2 latency in
the over-50 group compared to the under-50 group with the low and high noise. P1
latency did not show comparable findings. The increase in latency of the later
component of the CAEP in normal hearing subjects over 50 years of age, suggests a
degenerative process in the auditory pathway that occurs even prior to the onset of
hearing loss. This change may lead to impairment of speech discrimination abilities,
especially in difficult listening situations (cocktail party effect).
