Contribution of multiple pathways to the relationship between visual impairment and depression : Explaining mental health inequalities among older Chinese adults

BACKGROUND: Though visual impairment is a strong predictor for late-life depression, the underlying mechanisms remain unclear. This paper investigated the contribution of material, psychosocial and behavioural pathways in mediating a vision-depression association. METHODS: The study used cross-sectional data from the WHO Study on Global AGEing and Adult Health (SAGE), including 11,531 older Chinese adults. Depression was assessed based on an adaptation of the ICD-10 diagnostic criteria. Causal mediation analyses using inverse odds ratio weighting (IORW) approach were conducted to assess the mediating roles of material (wealth quintiles and perceived income inadequacy), behavioural (leisure activity, BMI and sleep) and psychosocial factors (social participation, trust and sense of safety). RESULTS: The participants with visual impairment had a 43% higher odds of depression than those with normal vision. In the mediation analysis, the material pathway contributed the most to the total effect, accounting for 31.7% of it. The proportion of the total effect which was mediated by psychosocial and behavioural factors was 24.2% and 22.5% respectively. When these three mediators were considered together in the full model, they accounted for 43.5% of the total effect of visual impairment on depression. LIMITATIONS: There still existed unexamined mediating factors. The cross-sectional study design might restrict temporal sequence. CONCLUSION: Visually-impaired population as high-risk group should be provided better access to screening, diagnosis and treatment of depression. Material, behavioural and psychosocial factors may serve as relevant points of entry for developing intervention programmes to improve the mental health conditions of visually-impaired people