Relationship between physical activity and depressive symptoms in older Korean adults: moderation analysis of muscular strength

Background: This population-based cross-sectional study examined the associations between physical activity (PA) and lower body muscle strength (LBMS) with late-life depression in a representative sample of older Korean adults aged 65 years and older. Methods: The data used in the current study (n=10,097/60% women) were extracted from the 2020 Korea Longitudinal Study on Aging, which is a nationwide population-based survey conducted in Korea. Depressive symptoms were assessed with the Geriatric Depression Scale Short-Form. PA and LBMS were evaluated with a self-reported questionnaire and the 5 times sit-to-stand test, respectively. Covariates include age, gender, body mass index, education level, smoking status, alcohol intake, and comorbidity. Results: Insufficient PA had higher odds of depression (odds ratio [OR] = 1.201, 95% confidence interval [CI] = 1.035-1.393, p = 0.016), even after adjustments for all covariates, compared to sufficient PA. Poor LBMS had higher odds of depression (OR = 2.173, 95% CI = 1.821-2.593, p < 0.001), even after adjustments for all covariates, compared to good LBMS. Particularly, a significant moderation effect of LBMS on the relationship between PA and depressive symptoms was observed (beta = 0.3514 and 95% CI = 0.1294 similar to 0.5733, p < 0.001). Individuals with poor LBMS had a greater odd of depression associated with physical inactivity compared to their counterparts with good LBMS. Conclusions: The results of this study support the importance of promoting muscular strength through regular exercise as a preventive strategy against late-life depression in Korean adults.