Association between functional disability and long-term trajectories of depressive symptoms: Evidence from the China Health and Retirement Longitudinal Study

BACKGROUND: Prior research has suggested that functional disability was associated with increased risk of incident depressive symptoms in the elderly. However, little is known about the potential role of functional disability on the long-term trajectories of depressive symptoms among middle-aged and older Chinese adults. METHODS: Data were drawn from the China Health and Retirement Longitudinal Study. A total of 8415 participants with up to four measurements of depressive symptoms assessed by the Center for Epidemiologic Studies Depression Scale (CESD) were included. Functional disability was evaluated by activities of daily living (ADLs) and instrumental ADLs (IADLs) at baseline. We identified the trajectories of depressive symptoms over 7-year follow-up using group-based trajectory modelling, and examined the association between functional disability and depressive symptom trajectories using multinomial logistic regression. RESULTS: We identified four trajectories of depressive symptoms throughout the follow-up, characterized by maintaining a low CES-D score (low symptoms); maintaining a moderate CES-D score (moderate symptoms); increasing progressively and reaching a high CES-D score at the end of follow-up (increasing symptom); and increasing quickly and maintaining a high CES-D score (high symptoms). We found that participants with severe functional disability were at increased likelihood of being in the moderate (odds ratio [OR] = 2.27, 95% confidence interval [CI] 1.68-3.07), increasing (OR = 2.31, 95% CI 1.49-3.59), and high (OR = 4.74, 95% CI 3.07-7.31) depressive symptom trajectories. LIMITATIONS: Depressive symptoms and functional disability were evaluated based on self-reported scales. CONCLUSIONS: Our findings suggest that functional disability was associated with unfavorable depressive symptom trajectories among middle-aged and older Chinese adults.