Residential greenness and blood lipids in urban-dwelling adults: the 33 Communities Chinese Health Study

While exposure to places with higher greenness shows health benefits, evidence is scarce on its lipidemic effects. We assessed the associations between residential greenness and blood lipids and effect mediations by air pollution, physical activity, and adiposity in China. Our study included 15,477 adults from the population-based 33 Communities Chinese Health Study, conducted between April and December 2009, in Northeastern China. We measured total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C). Residential greenness was estimated using two satellite-derived vegetation indices - the Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI). We used both nitrogen dioxide (NO) and particles ≤2.5 μm in aerodynamic diameter (PM) as proxies of outdoor air pollution. Associations were assessed using linear mixed effects regression models and logistic mixed effects regression models, and mediation analyses were also performed. Living in higher greenness areas was consistently associated with lower TC, TG, and LDL-C levels and higher HDL-C levels (e.g., change in TC, TG, LDL-C, and HDL-C per 0.1-unit increase in NDVI was\ua0-1.52%,\ua0-3.05%,\ua0-1.91%, and 0.52%, respectively). Similar results were obtained for the corresponding dyslipidemias. These associations were generally stronger in women and older adults. While educational levels showed effect modifications, the effect pattern was inconsistent. Both outdoor air pollution and body mass index mediated 9.1-62.3% and 5.6-40.1% of the associations for greenness and blood lipids, respectively, however, physical activity did not. Our results suggest beneficial associations between residing in places with higher greenness and blood lipid levels, especially in women and the elder individuals. The associations were partly mediated by lower air pollution and adiposity