Ziqing Qiao ^1* Zichun Wang ^2* Jiaping Qiu ^1* Jie Zhang ^1* Weiyi Cao ^1*

• ¹ Nanqiao Community Health Service Center, Shanghai, China
• ² Fengxian District Animal Disease Prevention and Control Center, Shanghai, China

Background: Anxiety and depression are serious psychological and public health issues among the elderly. Currently, there is a lack of understanding of the relationship between Body Mass Index (BMI) and anxiety or depression symptoms in the elderly population in China. Therefore, the purpose of this study is to investigate the impact of BMI on anxiety and depression through correlation analysis in different subgroups and to examine the potential chain mediating effects of Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) between BMI and symptoms of anxiety and depression. Methods: From the CLHLS database conducted in 2017-2018, data regarding height, weight, anxiety symptoms, depression symptoms, as well as demographic, socioeconomic, behavioral, and health-related characteristics were collected. Multivariate logistic regression analysis was used to explore the impact of BMI on anxiety and depression symptoms. Finally, the SPSS macro process was utilized to test the multiple mediating effects of ADL and IADL between BMI and anxiety or depression symptoms. Results: After screening, a final sample of 9098 Chinese elderly individuals aged 65 and above was selected. Among them, 1074 cases (11.8%) exhibited anxiety symptoms, 1458 cases (16.0%) exhibited depressive symptoms. Compared to normal BMI, the adjusted analysis showed that underweight in Chinese elderly individuals was significantly associated with anxiety (OR=1.316, P=0.004) and depression (OR=1.232, P=0.013). This relationship was found to be more significant in males, individuals aged 80 and above, unmarried individuals, and those residing in town. ADL and IADL played a chain-mediated role between BMI and anxiety symptoms in the elderly. BMI not only had a direct effect on anxiety symptoms in the elderly (effect=-0.0159; SE=0.0066; 95%CI: LL=-0.0288, UL=-0.0031), but also influenced them indirectly through two pathways: the independent mediating role of IADL (effect=-0.0010; SE=0.0005; 95%CI: LL=-0.0018, UL=-0.0003) and the chain-mediated role of ADL and IADL (effect=-0.0012; SE=0.0004; 95%CI: LL=-0.0020, UL=-0.0006). Conclusions: In the elderly individuals in China, underweight is associated with an increased risk of anxiety and depression symptoms. Improving the underweight condition of Chinese elderly individuals can reduce their ADL and IADL limitations, thereby benefiting their mental health.