In elderly people both a decline in time spent in SWS and a
decrease of REM sleep have been reported (6,7). Moreover,
nocturnal GH secretion is known to be reduced in elderly as
compared to young subjects (6,8). However, results are
inconsistent regarding the basal cortisol secretion in elderly
people. Pavlov et al. (9) reported on elevated basal cortisol
levels in elderly men awake in the evening, whereas other
studies failed to find any effect of age on cortisol concentrations
measured in the morning (10,11). However, in the
morning, pituitary-adrenal secretion is activated due to its
circadian rhythm (12). The cortisol nadir in the beginning of
nocturnal sleep therefore may represent a more valid estimate
of basal secretory activity of this system (13). Moreover,
during sleep, assessment of basal cortisol levels is least
contaminated by stress-related activity of the pituitaryadrenal
axis to external stimuli.