Napping and 24-hour sleep/wake patterns in healthy elderly and young adults

Abstract

Objective: To examine differences between healthy elderly and young adults in daytime napping, nocturnal sleep, and 24-hour sleep/wake patterns. A second objective was to determine whether elderly subjects with more and less frequent naps differed in their clinical features or nocturnal sleep.

Design: Survey by sleep/wake logs and polysomnography. Comparison by age.

Setting: Sleep/wake logs were completed in the subjects' homes. Polysomnographic studies were conducted on an outpatient basis in a sleep and chronobiology research laboratory.

Subjects: Convenience samples of forty-five healthy subjects over 78 years of age (21M, 24F) and 33 healthy adults between 20 and 30 years of age (20M, 13F).

Main outcome measures: Using self-reports, we estimated the frequency and timing of daytime naps; timing, duration, and quality of nocturnal sleep; and 24-hour patterns of sleep and wakefulness. Also polysomnographic sleep measures.

Results: Compared to young adults, elderly subjects reported a greater mean number of daytime naps (P = .004), shorter nocturnal sleep with more wakefulness and earlier sleep hours (P less than .003 for each), and a trend for a shorter 24-hour sleep fraction. Among the elderly, more-frequent and less-frequent nappers did not differ in clinical ratings, self-report sleep measures, or polysomnographic measures. There was a trend for more sleep-disordered breathing and periodic limb movements in more frequent nappers.

Conclusions: These findings are consistent with an age-related decrease in amplitude of the circadian sleep propensity rhythm, or with the expression of a semi-circadian (12-hour) sleepiness rhythm. However, we cannot exclude the additional possibility that napping results from lifestyle factors and nocturnal sleep pathologies in a subset of the elderly.