CHARLS insights into the impact of dual interactions of chronic diseases on depression in middle-aged and elderly individuals

Depression and chronic diseases are closely linked, but the combined impact of multiple chronic diseases on depression is not well understood due to limited research on their interaction. This study aimed to examine how the interaction of chronic diseases influences depression in middle-aged and elderly individuals, and to identify high-risk factors for depression related to these disease interactions. In this study, depression among middle-aged and elderly individuals was designated as the dependent variable. The dataset from the 2015 China Health and Retirement Longitudinal Study (CHARLS) underwent both univariate and multivariate analyses. Subsequently, a dual interaction analysis was performed to examine the significant impact of the number of chronic diseases on depression, complemented by an attribution analysis. Among the 8163 participants, depression was more common in females, unmarried individuals, rural residents, and non-retired (P < 0.05, 0.01 or 0.001). Higher education correlate with lower depression rates. Participants with chronic diseases show higher depression rates than those without (P < 0.05, 0.01, or 0.001). The depression group exhibited lower episodic memory, cognitive ability, and sleep duration (P < 0.05, 0.01, or 0.001). Various factors significantly contribute to depression in middle-aged and elderly individuals (P < 0.05, 0.01 or 0.001). Finally, the majority of chronic diseases have a significant contribution to the occurrence of depression in middle-aged and elderly individuals after dual interaction. Chronic diseases significantly influence depression in middle-aged and elderly individuals, with their dual interaction having a complex effect. While most chronic disease indicators aren't useful for diagnosing depression, memory and cognitive function indicators can help. These should be considered alongside other chronic disease indicators when diagnosing depression.