Abstract
OBJECTIVE: To determine if physical activity increase at midlife is associated with less cognitive decline over time. METHODS: The Study of Women's Health Across the Nation, an ongoing longitudinal study, started in 1996 with a diverse cohort of midlife women, and. Included cognitive and physical activity tests. Analytic baseline for physical activity was the average of visits zero through six, prior to cognitive testing. Women missing educational levels or baseline stroke, or fewer than two baseline physical activity or three cognitive assessments, were excluded. Change in physical activity was calculated as difference between metabolic equivalent of task (MET) hours at analytic baseline and visits nine, 12, 13, and 15 (2017). Cognitive baseline was defined at visit nine to reduce practice effects. Longitudinal association between physical activity change and cognition for processing speed [Symbol Digit Modalities Test (SDMT)], working memory [Digit Span Backwards (DSB)], and verbal episodic memory [East Boston Memory Test- delayed recall (EBMT-d)] were analyzed using mixed linear and Poisson regression models. RESULTS: Our sample consisted of 2020 women. Baseline MET hours/week was Mean (SD) 6.8 (2.4). Increases in MET hours/week from physical activity baseline was positively associated with higher SDMT scores over time, adjusting for sociodemographic, medical, and emotional-behavioral factors [β = 0.02 (0, 0.04)]. No significant associations were observed for the other two measures. CONCLUSION: Physical activity increase was associated with higher processing speed over time but not with working or verbal episodic memory. Increased physical activity in midlife women may delay cognitive decline.