Sleep/wake cycle and physical activity in healthy elderly people.

Investigations concerning the temporal organization of the sleep/wake cycle (SWC) in healthy active elderly, specially focusing possible relationships between regular daily routines, sleep fragmentation and sleep quality in aging are still scarce. We studied the SWC of 23 healthy active elderly (65-76 years old) of both sexes (15 female, 8 male), engaged in an exercise program for old people, considering that physical exercise sessions could represent a strategy for keeping structured daily routines. We report the relationships between SWC characteristics and performance of physical exercises viewed as time cues. We collected SWC data by means of sleep logs and data about light exposition by means of actigraphy during 23 consecutive days. Individuals who chose earlier times for exercising showed longer exposition to natural bright light and reported better sleep quality. Indications that physical exercises could be beneficial upon sleep were scarce (better subjective sleep quality). Strength of semicircadian component of the SWC was greater for subjects who exercised longer, suggesting they have advantageously used naps as part of their active and healthy lifestyle, and indicating the need for studying more closely the temporal organization of naps.