Interplay of Physical Activity, Muscle Strength, and Depression in Cognitive Impairment among Korean Older Adults: A Cross-sectional Study

OBJECTIVE: The present study was to investigate the association of physical activity (PA), relative-handgrip strength (RHGS), depressive symptoms, and cognitive impairment in Korean older adults. METHODS: This study included 512 community-dwelling Korean older adults (417 female, 95 male) aged ≥ 65 years (74.8 ± 5.4 years). PA and RHGS were assessed using an accelerometer and dynamometer, respectively. Depressive symptoms were evaluated by the Korean form of the Center for Epidemiologic Studies Depression (CES-D) Scale. Cognitive impairment was assessed through the Mini-Mental State Examination for Dementia Screening (MMSE-DS). RESULTS: Multiple logistic regression analysis revealed that depressive symptoms (odds ratio [OR] = 2.676, 95% confidence interval [CI]: 1.594-4.492, p < 0.001) showed a significant association with increased odds of cognitive impairment compared with normal depression status (OR = 1). Depressive symptoms had both direct and indirect effects on cognitive impairment. Both PA and RHGS partially mediated the relationship between depressive symptoms and cognitive impairment (PA: effect [B] = -0.017, 95% CI: -0.028 to -0.009, p < 0.001; RHGS: B = -0.005, 95% CI: -0.007 to -0.003, p < 0.001). Serial mediation analysis further indicated that the association between depressive symptoms and cognitive impairment was sequentially mediated by PA and RHGS (B = -0.004, 95% CI: -0.006 to -0.002, p < 0.001). CONCLUSION: Promoting PA among older adults may be crucial, as this helps improve and maintain muscular strength and mitigates the negative impact of depressive symptoms on cognitive impairment.