Age differences in sleep-wake behavior under natural conditions

Differences in lifestyle may account for a considerable portion of the reported age-related changes in overt circadian rhythmicity. By instructing a group of healthy, noninstitutionalized, elderly males (aged 59-74 yrs) and a group of young male adults (aged 18-26 yrs) to keep a sleep-wake log for a period of 2 wks, and to wear an activity monitor for an overlapping period of 11 days, the authors attempted to assess age-related differences in the habitual sleep-wake behavior, in particular its day-to-day variability. Four clusters of coherent variables were constructed, reflecting (1) circadian phase, (2) variability of sleep-wake behavior, (3) sleep-wake continuity and (4) subjective sleep-wake quality. The results show that, in comparison with the young Ss, the elderly had a relatively advanced and more regular sleep-wake pattern, reported more midnight awakening, and did not differ in their subjective sleep evaluation. In spite of a greater regularity in their lifestyle (which would favor a larger amplitude of the overt circadian rhythmicity), oral temperature measurements showed some evidence of a weakened 24 hr periodicity in the elderly.