Increased fragmentation of rest-activity patterns is associated with a characteristic pattern of cognitive impairment in older individuals.

STUDY
OBJECTIVES: Aging is accompanied by changes in cognitive function, and changes in rest-activity patterns. Previous work has demonstrated associations between global rest-activity measures and cognitive performance on a number of tasks. Recently, we demonstrated that aging is associated with changes in the minute-to-minute fragmentation of rest-activity patterns in addition to changes in amounts of rest and activity. Given the body of experimental evidence linking sleep fragmentation with decrements in cognitive function in animals and humans, we hypothesized that increased fragmentation of rest-activity patterns would be associated with decreased cognitive function in older individuals.
DESIGN: Cross-sectional. PARTICIPANTS: 700 community-dwelling individuals from the Rush Memory and Aging Project. MEASUREMENTS AND
RESULTS: We obtained up to 11 days of actigraphic recordings in subjects' home environments and quantified the fragmentation of rest and activity using a recently developed state transition metric. We tested the associations between this metric and performance in 5 cognitive domains. Greater fragmentation of both rest and activity were associated with lower levels of cognitive performance, and this association was independent of total amounts of rest or activity. There was a characteristic pattern of cognitive deficits associated with rest and activity fragmentation, with preferential involvement of perceptual speed, semantic memory, working memory, and visuospatial abilities, and relative sparing of episodic memory.
CONCLUSIONS: The fragmentation of periods of rest and activity is a clinically important characteristic of rest-activity patterns that correlates with cognitive performance in older individuals.