Residential greenness and dyslipidemia risk: Dose-response relations and mediation through BMI and air pollution

Background: Evidence on associations of residential greenness with dyslipidemia is limited, particularly regarding dose-response relations and mediation. Objectives: To investigate associations between greenness and dyslipidemia, non-linear dose-response relation-ships and mediators. Methods: This cross-sectional study draws on the 2018 Fujian Behavior and Disease Surveillance (FBDS) cohort that used multi-stage stratified random sampling from the general population of Fujian Province, China. Par-ticipants with one or more abnormities in total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), or low-density lipoprotein cholesterol (LDL-C) were classified as having dyslipidemia. Residential greenness was operationalized as 3-year average of the normalized difference vegetation index (NDVI500m) and enhanced vegetation index (EVI500m). A doubly robust approach was used for effect quantifi-cation. Dose-response relations were studied with natural cubic splines. Mediation via physical activity (PA), body mass index (BMI), PM2.5, PM10, SO2, and NO2 was also examined. Results: Data from 43,183 participants were analyzed. Increases in NDVI500m and EVI500m residential greenness were associated with decreased dyslipidemia risk and improved blood lipids. Non-linear dose response re-lationships were discovered. Significant reduction of dyslipidemia risk was observed at levels of EVI500m > 0.48 and NDVI500m > 0.65. Joint mediation effects of PA, BMI, PM2.5, PM10, NO2, and SO2 on the associations of NDVI500m and EVI500m with dyslipidemia risk were 49.74% and 44.64%, respectively. Conclusions: Increased residential exposure to greenness was associated with decreased risk of dyslipidemia. A non-linear dose-response relationship between greenness and dyslipidemia suggests that specific thresholds of greenness need to be reached in order to achieve effects. BMI, PM2.5, and PM10 partially mediated the association.