The role of sleep and physical activity in cognitive decline: direct and mediating effects on executive control

[摘要] Adults often exhibit a marked decline in cognitive function with aging. However, some adults show remarkable abilities to maintain cognitive function into older adulthood. There is increasing evidence that healthy lifestyle factors, such as sleep quality and physical activity, may benefit cognition in older adults. However, the pathway through which physical activity benefits cognition is unknown. Given that physical activity improves sleep (Lopez, 2008), and sleep often benefits cognition (Goel, Rao, Durmer, & Dinges, 2009), sleep may mediate the relationship between physical activity and cognition (Vitiello, 2008). The present study examined individual differences in sleep quality and executive function in young and older adults. Subjects wore an accelerometer armband for one week, which estimated minutes of physical activity and sleep. These estimates were used to calculate objective sleep quality operationalized as sleep efficiency (total time asleep/total time lying down) and physical activity, operationalized as average metabolic equivalents (METs) while awake ('awake METs”). Using a task-switching paradigm, which manipulated time to prepare, Study 1 showed that subjects with high sleep efficiency maximized time to prepare more so than subjects with low sleep efficiency. In Study 2, after controlling for age, gender, and education, sleep efficiency was a significant mediator of the relationship between awake METs and cognitive performance in terms of switching, inhibition, working memory, and memory retrieval: all executive functions that show age-related decline. Thus, the relationship between physical activity and cognition may be driven by sleep quality. In Study 3, time of day was shown to influence whether older adults exhibited impaired performance relative to young adults. Additionally, this effect applied specifically to older adults with low sleep efficiency. This finding suggests that sleep quality combined with time of day are important factors in whether or not older adults exhibit cognitive impairments.

[发布机构] the University of Pittsburgh