Socioeconomic status and depressive symptoms in older people with the mediation role of social support: A population-based longitudinal study

Background Depressive symptoms has become an increasingly important public health issue, contributing to disability and disease burden around the world. Higher socioeconomic status (SES) has been found to be associated with lower prevalence of depression, but there are few studies about the older Chinese adults with long-term follow up and rigorous prospective design. Meanwhile, there is little conclusive evidence about the mechanisms through which SES influences the onset of depressive symptoms. Objective To prospectively examine the association of baseline socioeconomic factors with the risks of developing depressive symptoms during 7-year follow up in older Chinese population, and to study the mechanism by which SES impacts the prevalence of depressive symptoms. Methods A total of 5677 individuals over 45 years who participated in an ongoing nationally representative prospective cohort study, China Health and Retirement Longitudinal Study, were free from depressive symptoms at baseline, and completed 7-year follow-up were included. Depressive symptoms were assessed using the 10-item Center for Epidemiological Studies Depression Scale score. Cox proportional hazards regression models were used to examine the association of SES and the incidence of depressive symptoms in 2011 to 2018. Generalized structural equation model was used to analyze the mediation effects of social support on the relation between SES and depressive symptoms. Results During the 7-year follow-up, 2398 (42.2%) cases were identified as depressive symptoms. Compared with the lowest level of household income, participants with the highest level of household income had a 20% reduction in risk (95% CI, 0.70-0.92, P < 0.001). Participants who had junior high school or above education had a 41% lower risk of depressive disorders compared with illiterate participants (95% CI, 0.52-0.69, P < 0.001). The relationship between SES and depressive symptoms was partially mediated by the social support, where higher social support was negatively associated with depressive symptoms. The proportion of mediation effect was even larger for women compared with men. Conclusion Socioeconomic factors were independently associated with the development of depressive symptoms, and the relationship was partially mediated by social support. Social support could be an effective intervention to alleviate the negative effects of lower SES on mental health. Multiple-level policies should precisely target low-SES groups, and timely intervention to promote social support for this group should be used to reduce the influence of depression on individuals, family as well as the whole society.