Chronic pain, depression, and cognitive trajectories in Chinese middle-aged and older adults: A longitudinal cohort study

BACKGROUND: Chronic pain (CP) and depression are prevalent in aging populations, yet their combined effects on cognitive trajectories remain insufficiently explored in Chinese adults. This study aimed to identify distinct cognitive trajectory patterns and evaluate the independent and combined effects of CP and depression on cognitive decline. METHODS: Using data from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2015), we analyzed 7671 participants aged ≥45 years. Group-based trajectory modeling (GBTM) classifies participants into trajectory groups based on repeated assessments of global cognitive scores. Multivariable-adjusted multinomial logistic regression examined associations between CP, depression, and trajectory memberships, adjusting for sociodemographic, lifestyle, and health-related covariates. RESULTS: Three cognitive trajectories emerged: low (n = 1031, 13.93%), moderate (n = 3097, 40.57%), and high (n = 3543, 45.50%). CP was independently associated with increased odds of belonging to the low (OR = 1.95, 95% CI: 1.64-2.31) and moderate (OR = 1.49, 95% CI: 1.32-1.67) trajectories. The low trajectory group was characterized by older age, rural residence, lower education, and more severe depressive symptoms. CP severity exhibited a dose-dependent relationship, with severe pain showing the strongest association with the low cognitive trajectory group (OR = 2.11, 95% CI: 1.63-2.73). Participants with coexisting CP and depression experienced accelerated cognitive decline compared to those without either condition (P < 0.001). CONCLUSIONS: CP and depression are independent and synergistic risk factors for cognitive decline in Chinese middle-aged and older adults. Early screening and integrated interventions targeting both conditions can mitigate cognitive deterioration in aging populations.