Pollution, hazards, and health inequalities: a longitudinal exploration of the impact of PM2.5 on depression among rural older adults with different incomes in China

Air pollution has been increasingly associated with heightened mental health risks. However, there is a scarcity of nationwide research addressing the mental health issue of rural older adults, as well as a lack of thorough investigations into the underlying issues of health inequality. This study leverages data from the 2014-2018 "China Longitudinal Ageing Social Survey" to conduct a comprehensive longitudinal analysis utilizing latent growth models and random intercept cross-lagged panel models. The findings reveal a concerning trend of worsening depressive symptoms among rural Chinese older adults, with an average annual growth rate of 1.9%. PM2.5 concentrations significantly contribute to depression in this population. PM2.5 pollution exhibit a indicative association with depressive symptoms in the lagged periods, with standard influence coefficients of 0.089 and 0.073, respectively. However, this association is only observed in middle- and low-income groups, with no evidence found in high-income groups. Data suggest that lower income levels heighten vulnerability to the adverse effects of PM2.5 on mental health, with low-income rural older adults being the most severely affected subgroup. This implies that there are health inequalities related to the impact of air pollution among elderly populations of different income levels. Consequently, targeted interventions aimed at addressing the disparities in rural are essential for mitigating these inequalities and improving health outcomes in this vulnerable population.