Individual and joint associations between sleep duration and physical activity with cognitive function: A longitudinal analysis among middle‐aged and older adults in China

Abstract INTRODUCTION Studies using cross‐sectional data or with a short follow‐up period fail to distinguish whether the associations between sleep duration and physical activity with cognitive function result from reverse causation. METHODS The longitudinal study examined the individual and joint associations, with specific temporality, between sleep duration and physical activity with cognitive function, using time‐lagged linear mixed models and generalized additive mixed models. RESULTS A total of 14,694 participants aged ≥ 50 years were included, with an average lagged time of 4.5 (standard deviation 1.3) years. Long sleep duration was independently associated with cognitive decline, while short sleep duration and physical activity were not. The analysis of joint effects showed that increased physical activity slowed the rate of cognitive decline among participants reporting long sleep duration, consistent with the results of the stratified analyses. DISCUSSION Interventions on improving sleep should consider concurrent physical activity to maximize benefits for slowing cognitive decline. Highlights Long sleep duration was independently associated with worse cognitive function, while short sleep duration was not. Elevated levels of physical activity were not independently associated with better cognitive function. Increased physical activity appeared to mitigate the negative impact of long sleep duration on cognitive function.