Abstract
This study aims to evaluate the independent and interactive effects of multimorbidity and cognitive impairment on depressive symptoms among older adults in China. Employing a cross-sectional design, the study collected data from 10,369 individuals aged 65 and above across 35 communities/villages in China. Depressive symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9), cognitive function was evaluated with the Alzheimer's Disease-8 (AD-8) scale, and chronic disease conditions were recorded. The results indicated that older adults with multimorbidity (OR = 2.481, 95% CI: 2.117, 2.908) and those at high risk of cognitive impairment (OR = 5.469, 95% CI: 4.644, 6.441) exhibited a higher likelihood of experiencing depressive symptoms. Further interaction analysis revealed that, after controlling for confounding factors, no significant multiplicative interaction was found between multimorbidity and cognitive impairment (P = 0.581); however, a significant additive interaction effect was observed (OR = 13.809, 95% CI: 11.063, 17.237). These findings suggest that multimorbidity and cognitive impairment are important factors associated with depressive symptoms in older adults, and their combined presence is linked to a substantially increased likelihood of experiencing depressive symptoms compared to either condition alone.