Physical Activity Trajectories, Autonomic Balance and Cognitive Function: the CARDIA Study

Abstract

AbstractBackgroundPhysical activity (PA), and particularly moderate to vigorous intensity PA (MVPA), may protect against cognitive decline. However, the underlying mechanisms are not fully understood. Cardiac autonomic balance is influenced by PA and implicated in dementia pathogenesis. Therefore, the study aimed to examine whether autonomic balance mediates the association between PA and cognitive function.MethodThe sample included 1,939 participants from the Coronary Artery Risk Development in Young Adults (CARDIA) study. MVPA was obtained in 7 consecutive examinations from baseline (1985‐86; 18‐30 years) to the Year 20 exam. Cardiac autonomic balance was assessed at Year 20 via resting heart rate, and via measures of heart rate variability: standard deviation normal to normal (SDNN) and root mean square of successive differences (RMSDD). A comprehensive cognitive assessment was performed at Year 30. Group‐based trajectory modeling was used to identify homogenous MVPA trajectory groups, and formal mediation analysis was used to test whether cardiac autonomic function indices lie on the causal pathway between MVPA trajectories and cognitive function.ResultThree distinct PA trajectory patterns were identified: (1) Below MVPA guidelines (n = 1,122; 57.9%); (2) Meeting MVPA guidelines (n = 652; 33.6%); and (3) Exceeding MVPA guidelines (n = 165; 8.5%) (Figure). Meeting and exceeding MVPA guidelines were related to lower resting heart rate and higher heart rate variability, which indicate improved autonomic balance. Meeting and exceeding MVPA guidelines were additionally associated with improved semantic fluency performance. The association between higher MVPA level and semantic fluency performance was fully mediated by RMSDD and partially mediated by SDNN. No additional associations were observed between MVPA trajectories and other cognitive outcomes, and no statistically significant mediation by autonomic balance indices was found for these associations (Table).ConclusionHigher MVPA levels across the young adult to midlife transition were associated with better cardiac autonomic function, which in turn explained some of the associations between PA trajectories and better semantic fluency performance. Future studies, particularly among older individuals are warranted to clarify the role of autonomic balance in the link between physical activity and brain health. These findings may lead to more targeted PA recommendations across the life‐course to slow cognitive decline and decrease dementia risk.