Isotemporal substitution modeling on sedentary behaviors and physical activity with depressive symptoms among older adults in the US: The national health and nutrition examination survey, 2007-2016

Background: Late-life depression is a great burden of public health. Previous studies reported that physical activity is associated with reduced depressive symptoms among older adults, while the competing nature of physical activity and sedentary behaviors has been largely neglected in studies. We aimed to examine the associations of replacing sedentary behaviors with walking/bicycling or moderate-to-vigorous physical activity (MVPA) with depressive symptoms in older adults. Methods: A cross-sectional analysis was conducted among 8374 older adults (60 years or older) included in the National Health and Nutrition Examination Survey (NHANES), 2007-2016. The Global Physical Activity Questionnaire was used to measure self-reported time for sedentary behaviors, walking/bicycling, and MVPA. The 9-item Patient Health Questionnaire was used to measure depressive symptoms (including overall, somatic, and cognitive). Z-scores were created for depressive symptoms. Isotemporal substitution models using multivariable linear regression were applied to examine the associations of sedentary behaviors, walking/bicycling, and MVPA with z-scores of depressive symptoms. Results: Replacing 30 min/day sedentary behaviors with 30 min/day of MVPA (beta (beta) = -0.10, 95% confidence interval (CI): -0.14, -0.06) or 30 min/day of walking/bicycling (beta = -0.04, 95% CI: -0.06, -0.02) was associated with lower z-score for depressive symptoms. Replacing 30 min/day of walking/bicycling for 30 min/day of MVPA was associated with lower z-score for depressive symptoms (beta = -0.06, 95% CI: -0.10, -0.02). Limitations: A cross-sectional study design precludes causal inferences. Conclusion: Replacing sedentary behaviors with walking/bicycling or MVPA is associated with lower depressive symptoms among older adults. Future research is expected to investigate the effectiveness of physical activity on prevention and treatment of late-life depression.