A Reverse J-Shaped Association Between Total Physical Activity and Cognitive Impairment in Older Chinese Adults: Evidence from a Nationally Representative Cross-sectional Study Using CHARLS Data

Background: Cognitive impairment (CI) is a growing concern in aging societies, particularly in low- and middle-income countries. Although physical activity (PA) is widely recognized as neuroprotective, its optimal dose for cognitive health remains uncertain. Objective : To evaluate the nonlinear association between total physical activity (TPA) and cognitive impairment in older Chinese adults, and to examine whether depressive symptoms and life satisfaction mediate this relationship. Methods: We analyzed data from 7,818 adults aged ≥60 years in the China Health and Retirement Longitudinal Study (CHARLS, 2011–2020). Total physical activity (TPA) was assessed using the long-form IPAQ and expressed in MET-minutes/week. CI was defined as a total cognitive score <10. Logistic regression, restricted cubic spline models, and structural equation modeling (SEM) were used to examine nonlinear associations and psychological mediation pathways, adjusting for demographic and health covariates. Results: We observed a reverse J-shaped association between TPA and CI risk, with the lowest odds at ~2,800 MET-min/week (OR = 0.772, 95% CI: 0.648–0.917). Excessive TPA was not associated with additional benefits and showed a trend toward increased risk. Mediation analysis revealed that depressive symptoms and life satisfaction partially accounted for the relationship. Conclusion: This study observed a statistically significant reverse J-shaped association between total physical activity and cognitive impairment in older Chinese adults, with the lowest risk occurring around 2,800 MET-minutes per week. Both insufficient and excessive activity levels were associated with higher cognitive risk, extending previous findings by quantifying this population's optimal activity range for cognitive health. Additionally, depressive symptoms and life satisfaction were identified as partial mediators, suggesting that psychological well-being may play a significant role in the pathway linking physical activity to cognitive outcomes among older adults.