Physical Activity Patterns and Variability, Cognitive Performance, and Dementia in the National Health and Aging Trends Study.

Introduction: Physical activity is a modifiable risk factor for dementia. However, the potential reverse effect of adverse cognitive change on physical activity remains underexplored.

Methods: Cross-sectional analysis of a subset of National Health and Aging Trends Study (NHATS; N = 706) U.S. Medicare beneficiaries. Dementia status (dementia vs. no dementia) was classified per NHATS protocol. Cognitive performance was assessed in executive function, orientation, and memory domains. Daily physical activity was assessed using wrist-worn accelerometers (Actigraph Insight).

Results: Compared with participants living without dementia, participants living with dementia had lower daily activity counts (×1000) (-319.3; 95% confidence interval (CI), -471.0 - -167.5), lower activity intensity (-1129.2 maximum counts per day; 95% CI, -1518.4 - -740.0 counts per day), less time spent active (64.3 min/day; 95% CI, 28.1-100.4 min/day), and more fragmented patterns of activity (6.1%; 95% CI, 3.0%-9.2%). One-unit higher cognitive performance in executive function was associated with higher daily activity counts (×1000) (67.9; 95% CI, 19.7-116.0), higher activity intensity (375.4; 95% CI, 232.0-518.7), more time spent active (12.4 min; 95% CI, 2.1-22.7 min), and lower fragmentation (-1.4%; 95% CI, -2.2% - -0.5%). One-unit higher orientation score was associated with higher daily activity counts (×1000) (61.0; 95% CI, 31.9-90.0), higher activity intensity (266.6; 95% CI, 197.9-335.2), more time spent active (11.6 min; 95% CI, 5.2-18.0 more active minutes), greater stability of daily activities (1.1; 95% CI, 0.3-1.9), and lower fragmentation (-1.2%; 95% CI, -1.7% - -0.7%). One-unit higher memory score was associated with higher daily activity counts (×1000) (28.1; 95% CI, 15.0-41.2), higher activity intensity (113.5; 95% CI, 77.0-150.1), and more time spent active (5.2 min; 95% CI, 2.4-8.0 min), as well as lower fragmentation (-0.5%; 95% CI, -0.7% - -0.3%).

Conclusions: In a nationally representative sample of older US adults, dementia and lower cognitive performance were associated with lower volume and intensity of daily physical activity, as well as more fragmented and less consistent patterns of physical activity. These associations emphasize the need for considering the impact of cognition on individuals' ability to engage in and maintain regular physical activity and suggest shifts in daily quantities and patterns of activity consistent with cognitive decline and dementia.