Exploring the Relationship between Physical Activity and Everyday Cognitive Function in Older Adults: Within- and Between- Person Variability

Research suggests that physical activity may play a role in preserving cognitive function in older adulthood. However, the exact nature, direction, and magnitude of observed associations remain unclear. The current study utilized a microlongitudinal design to repeatedly assess cognitive function and physical activity across five days. Two studies examined relationships between physical activity, physical fitness, and cognitive function among community-dwelling older adults. The first study examined associations between baseline performance in a measure of everyday cognition and multiple measures of physical activity and physical fitness. Bivariate analyses revealed that objectively measured physical activity of moderate-to-vigorous intensity, repeated chair stand time and 6-minute walk distance were significantly associated with everyday cognition. After adjusting for covariates in a multiple regression model, physical activity was not significantly associated with everyday cognition. However, a composite physical fitness score created from 6-minute walk distance and repeated chair stand time was significantly associated with DECA, and the full model accounted for 38% of the variance in baseline DECA performance.;The second study investigated within- and between-person relationships between daily physical activity and cognitive function. Study participants wore an activity monitor and completed a battery of cognitive assessments for five days. Multilevel modeling analyses indicated that same-day total number of steps was significantly associated with better visual speed of processing but not everyday cognition, or inductive reasoning. Time spent in moderate-to-vigorous activity was not significantly associated with same-day cognitive performance in any domain. However, previous-day moderate-to-vigorous physical activity was significantly associated with better inductive reasoning and speed of processing the following day, after controlling for age, gender and physical fitness. Time spent in moderate-to-vigorous activity explained 16% of the within-person variability in speed of processing. Physical fitness and age did not explain significant variability in between-person cognitive function.;Results obtained in the present study varied according to how physical activity and cognition were operationalized and measured. Associations between physical activity and cognition were more evident with moderate-to-vigorous activity, as opposed to total activity, and an acute temporal relationship was suggested, with better cognitive performance following engagement in moderate-to-vigorous physical activity. Results also indicated that within-person fluctuations in domains of cognitive performance were positively associated with physical activity, and were more pronounced with cognitively complex tasks that were timed.