Gender differences in the circadian temperature rhythms of healthy elderly subjects: relationships to sleep quality.

Body core temperature and subjective sleep quality were measured in 22 healthy elderly men and women while they lived at home and continued their normal daily activities. The acrophase of body temperature was phase-advanced by an average of 1.25 h in the older women compared to the age-matched men. Habitual bedtimes did not differ between men and women, but usual wakeup time and average sleep duration did: women awakened earlier and slept for shorter durations. Women were also less satisfied with their sleep than were the men. For the group, the acrophase of body temperature was significantly positively correlated with habitual bedtime and wakeup time. These data support the notion that age-related changes in the circadian timing system are, in large part, gender-dependent. The findings are also consistent with the hypothesis that alterations in sleep timing and quality that typically accompany aging are closely tied to age-related changes in circadian physiology.