Motor activity and sleep duration as a function of age in healthy men.

Patient activity monitors (PAM's) and self-report diaries were employed to examine wrist movements over a 9 day period in 43 healthy men aged 21 to 83 years, in their natural home and work environments. The mean sleep duration (from PAM) equaled 7.29 +/- 0.8 (S.D.) hr compared to 7.84 +/- 0.62 hr as estimated from the daily diaries. Neither parameter was correlated significantly with age (p greater than 0.05). Net activity counts per 24 hr day declined significantly with age (p less than 0.05), but the effect of age was small and accounted for only 15% of the variance. When the data from each age group were averaged into mean 24 hr days, it was found that: (1) the greatest reductions in the older subjects' activity occurred during evening hours; (2) differences between old and young subjects were more profound on weekends than on weekdays; and (3) only the young subjects' activity profiles differed between weekdays and weekends, as they rose from bed later on weekends. The results indicate that 24 hr activity can be quantified and characterized in natural work and home environments, in relation to diary information. Only small age differences occur in overall 24 hr activity in rigorously screened healthy men.