Can City Health Expenditure Alleviate Depression in Later Life? --The Mediating Role of Physical Activity in China

Background: Late-life depression is highly prevalent in China, affecting nearly 20% of older adults. While city-level public health expenditure is hypothesized to buffer mental health risks, the mechanisms remain unclear. This study explores the association between city-level public health expenditure and depressive symptoms among older Chinese adults, with a focus on the potential mediating role of physical activity. Methods: Using cross-sectional data of older adults across 295 Chinese cities in 2020, we applied fixed-effects regression and mediation analysis. Depressive symptoms were assessed via the CES-D scale, physical activity frequency was self-reported, and public health expenditure was measured as the proportion of city-level fiscal spending. Robustness checks included alternative measures, bootstrap resampling (1,000 replications), and model re-estimation. Results: Higher frequency of physical activity was significantly associated with fewer depressive symptoms (β = -0.32, p < 0.001). A greater proportion of public health expenditure also modestly associated with lower depressive symptoms (β = -0.10, p < 0.05). Mediation analysis suggested that physical activity accounted for approximately 18% of the overall association between health expenditure and depression (indirect effect = −0.06, 95% CI [−0.11, −0.01]). Results were robust to alternative specifications. Conclusion: Municipal health investment is modestly associated with lower depressive symptoms among older adults, partly through links with physical activity. Strengthening city-level preventive health programs and integrating exercise promotion into community health services may contribute to supporting healthy aging in China, though longitudinal research is needed to clarify causal pathways.