The relationship between chronic diseases and depression in middle-aged and older adults: A 4-year follow-up study from the China Health and Retirement Longitudinal Study.

Background: Evidence of the association between common chronic diseases and depression is sparse.

Methods: Totally 7819 participants aged 45+ without depression at baseline were followed-up (2011-2015) to detect incident depression. Chronic diseases and depression were defined by self-reported diagnosis and the Center for Epidemiological Studies Depression Scale (CES-D10), respectively. Cox proportional hazards model was used to explore the association between chronic diseases and depression adjusting for age, gender, education, marital/living conditions, area, smoking, drinking, economic status, BMI and health insurance.

Results: During an average of 3.42 years follow-up, 2271 participants developed depression (85 per 1000 person-year). Chronic diseases were related to significantly higher risk of depression (HR = 1.38). A higher risk of depression was also associated with specific diseases: stomach/other digestive diseases (HR = 1.19), diabetes (HR = 1.22), arthritis/rheumatism (HR = 1.30), and kidney diseases (HR = 1.34) (P < 0.05). The risk of depression increased with increasing in the number of chronic diseases (1: HR = 1.27, 2: HR = 1.49, and 3+: HR = 1.51, P-trend < 0.001). No significant difference was observed across age, gender, education, and area.

Limitations: Chronic diseases and depression were based on self-reported diagnosis and measurement scale, respectively, which could lead to information bias. Some unmeasured confounders might have biased the results.

Conclusions: The occurrence of depression in people aged 45+ is associated with number of chronic diseases in a dose-response fashion. These results may provide guidance on preventing depression and improving the quality of life in middle and late adulthood.