Associations between ambient particulate matter and lipid levels among patients with depression: A moderated mediation analysis of C-reactive protein and residential greenness.

Depression is associated with an elevated risk of dyslipidemia, with chronic low-grade inflammation recognized as a key mechanism. Ambient particulate matter (PM2.5 and PM10) can induce systemic inflammation and disrupt lipid metabolism, yet evidence among depressed populations remains limited. Residential greenness may mitigate these adverse environmental effects. This cross-sectional study included 532 adults with depression in Anhui, China. Individual exposures to ambient particulate matter and residential greenness (measured by the Normalized Difference Vegetation Index, NDVI) were estimated using satellite-based spatiotemporal models. Multiple linear regression and moderated mediation analyses were applied to examine the relationships among particulate matter exposure, C-reactive protein (CRP), residential greenness, and lipid parameters. After adjusting for demographic, behavioral, and clinical factors, each interquartile range (IQR) increase in 12-month PM2.5 exposure (16.6 μg/m3) was associated with higher total cholesterol (TC) (β = 0.099, 95%CI: 0.063, 0.135) and non-high-density lipoprotein cholesterol (non-HDL-C) (β = 0.179, 95%CI: 0.124, 0.235), along with lower HDL-C. Similar associations were observed for PM10. Mediation analyses indicated that CRP significantly mediated these relationships, accounting for approximately 16%-24% of the total effects. Moderated mediation analyses further showed that residential greenness significantly attenuated both the association between particulate matter and CRP and the subsequent relationship between CRP and lipid parameters. Conditional indirect effects were significant primarily in areas with lower greenness levels. Findings indicate that long-term exposure to particulate matter may contribute to lipid dysregulation in individuals with depression through systemic inflammation, while higher residential greenness may mitigate this pathway. Integrating environmental management strategies, including air pollution control and urban greening, may provide additional benefits for cardiometabolic health in populations with depression.