The Effects of an Afternoon Nap on Episodic Memory in Young and Older Adults.

STUDY OBJECTIVES

In young adults, napping is hypothesized to benefit episodic memory retention (eg, via consolidation). Whether this relationship is present in older adults has not been adequately tested but is an important question because older adults display marked changes in sleep and memory.

DESIGN

Between-subjects design.

SETTING

Sleep laboratory at Emory University School of Medicine.

PARTICIPANTS

Fifty healthy young adults (18-29) and 45 community-dwelling older adults (58-83).

INTERVENTION

Participants were randomly assigned to a 90-minute nap opportunity or an equal interval of quiet wakefulness.

MEASUREMENTS AND RESULTS

Participants underwent an item-wise directed forgetting learning procedure in which they studied words that were individually followed by the instruction to "remember" or "forget." Following a 90-minute retention interval filled with quiet wakefulness or a nap opportunity, they were asked to free recall and recognize those words. Young adults retained significantly more words following a nap interval than a quiet wakefulness interval on both free recall and recognition tests. There was modest evidence for greater nap-related retention of "remember" items relative to "forget" items for free recall but not recognition. Older adults' memory retention did not differ across nap and quiet wakefulness conditions, although they demonstrated greater fragmentation, lower N3, and lower rapid eye movement duration than the young adults.

CONCLUSIONS

In young adults, an afternoon nap benefits episodic memory retention, but such benefits decrease with advancing age.