Associations between positive affect and physical activity from young adulthood to midlife: A 25-year prospective study.

Objective: Positive affect may influence health by promoting physical activity, but evidence evaluating this association is mostly cross-sectional and cannot discern directionality. This study used a counterfactual-based framework to estimate the causal effect of positive affect on physical activity patterns over 25 years, accounting for potential reverse associations.

Method: Data were from 3,352 participants in the Coronary Artery Risk Development in Young Adults study. Repeated assessments of positive affect and physical activity were collected from 1990 to 2016. Longitudinal associations were evaluated in two ways: (a) using baseline positive affect in traditional linear mixed models that accounted for reverse causal associations by adjusting for baseline physical activity, and (b) using marginal structural models that treated positive affect as a time-varying exposure, thus accounting for dynamic reverse causal associations due to bidirectional relationships.

Results: Fully adjusted traditional models found no association with physical activity at the first follow-up assessment, but positive affect was related to a slower decline in physical activity over time. Marginal structural models similarly found that positive affect was unrelated to physical activity at the first follow-up assessment but robustly associated with a slower decline in activity levels (5-year change: β = -3.33, 95% confidence interval [CI] = -5.80, -0.86; difference in 5-year change per 1 - SD positive affect: β = 4.99, 95% CI = 2.52, 7.46).

Conclusions: Positive affect may play a causal role in slowing the decline in physical activity adults generally experience during through midlife. Efforts to enhance positive affect at the population level may be a promising new approach to help individuals stay active as they age. (PsycInfo Database Record (c) 2024 APA, all rights reserved).