Depression and Longitudinal Frailty Trajectories in Middle-Aged and Older Adults with Chronic Pain: A 8-Year National Cohort Study in China.

BACKGROUND: Global population aging is accelerating, and pain and depression frequently co-occur in middle-aged and older adults. Frailty, an age-related clinical syndrome, markedly elevates the risks of falls, disability, hospitalization, and mortality. This study investigated whether comorbid depression affects long-term frailty trajectories in patients with chronic pain, to help identify high-risk populations and guide comprehensive interventions. METHODS: Based on 8 years of follow-up (2011-2018) from the nationally representative multi-stage probability sample of the China Health and Retirement Longitudinal Study (CHARLS), 4,778 participants aged 45 years and older with chronic pain were enrolled. Depressive symptoms were assessed using the 10-item Center for Epidemiologic Studies Depression Scale (CES-D-10), with a total score ≥10 indicating depressive symptoms, and frailty was quantified by a 32-item Frailty Index (FI). Group-based trajectory modeling (GBTM) identified FI developmental trajectories, and multinomial logistic regression examined the association between depression and trajectory group membership. RESULTS: Three frailty trajectories were identified: Low Frailty Group, Moderate Frailty Group, and High Frailty Group. Overall, 61.3% of participants had comorbid depressive symptoms. Depressive symptoms were associated with significantly higher odds of the moderate (OR = 2.82, 95% CI 2.42-3.29) and high trajectories (OR = 6.57, 95% CI 5.18-8.34). Each 1-point CES-D-10 increment increased the odds by 11% and 19%, respectively. These associations remained stable across subgroups. CONCLUSION: In middle-aged and older adults with chronic pain, depression was associated with worsening frailty trajectories. Routine depression screening integrated with mental health care for chronic pain and frailty may help slow frailty progression and reduce disability burden.