Sleep, memory, and aging: the link between slow-wave sleep and episodic memory changes from younger to older adults.

In younger adults, recently learned episodic memories are reactivated and consolidated during slow-wave sleep (SWS). It is interesting that SWS declines across the life span, but little research has examined whether sleep-dependent memory consolidation occurs in older adults. In this study, younger adults and healthy older adults encoded word pairs in the morning or evening and then returned following a sleep or no-sleep interval. Sleep-stage scoring was obtained by using a home sleep-stage monitoring system. In the younger adult group, there was a positive correlation between word retention and amount of SWS during the retention interval. In contrast, the older adults demonstrated no significant positive correlations but one significant negative correlation between memory and SWS. These findings suggest that the link between episodic memory and SWS that is typically observed in younger adults may be weakened or otherwise changed in the healthy older adult population.