Associations of Physical Activity Trajectories With Transitions Across Cognitive States: A Multinational Cohort Study

OBJECTIVE: Physical activity (PA) has been identified as a major modifiable factor that protects against cognitive decline and dementia. This study examines the association between PA trajectories and cognitive state transitions in late life. METHODS: This study is a multinational cohort study, using data from HRS, ELSA, SHARE, and MHAS. PA trajectories were classified into two groups using group-based trajectory modeling (GBTM) based on PA intensity and frequency in each study. We applied a three-state model, defining State 1 as no cognitive impairment, State 2 as mild cognitive impairment (MCI), and State 3 as dementia. The MultiState Markov (MSM) model was used to assess the PA trajectory's effect. A meta-analysis was then conducted to provide an overall effect size across multinational cohorts. RESULTS: This study found that a higher PA trajectory was associated with a 25% lower risk of transitioning from no impairment to MCI (pooled HR = 0.75, 95% CI [0.65, 0.87], z = -3.93, p < 0.001) and a reduced risk of MCI progressing to dementia (pooled HR in the meta-analysis = 0.87, 95% CI [0.77, 0.98], z = -2.78, p = 0.01) though no significant effect on cognitive recovery from MCI in the meta-analysis. The meta-analytic results were mostly consistent with the individual results, showing moderate heterogeneity across studies for transitions from State 1 to State 2 (I² = 58.2%; Cochran's Q = 9.56, df = 4; p = 0.05) and from State 2 to State 1 (I² = 52.5%; Cochran's Q = 8.42, df = 4; p = 0.08), and low heterogeneity for State 2 to State 3 (I² = 30.9%; Cochran's Q = 5.79, df = 4; p = 0.22). The risk of progressing from no impairment to MCI decreased by 20% in the US, by 41% in Europe, and by 21% in Mexico, respectively. Additionally, the risk of MCI progressing to dementia was reduced by 19% in the US. CONCLUSIONS: These findings highlight a protective effect of higher PA trajectories in delaying the onset of MCI and dementia across multiple cohorts.