Background: Environmental factors play important roles in the development of cardiovascular disease, but evidence is lacking on the associations between residential greenness and ambient pollutants on the risk of cardiovascular disease related to glycolipid metabolism disturbance in individuals.
Objective: To investigate the independent and interactive effects of residential greenness and ambient pollutants on novel cardiovascular biomarkers related to glycolipid metabolism disturbance, including triglyceride-glucose (TyG) index, triglyceride (TG) to high-density lipoprotein cholesterol (HDL-c) ratio (TG/HDL-c), total cholesterol (TC) to HDL-c ratio (TC/HDL), and non-HDL-c.
Methods: We designed a repeated national cohort study of 5,085 adults from 150 counties across China. Levels of TyG index, TG/HDL-c, TC/HDL and non-HDL-c were measured at baseline (2011) and 4 years later (2015). Residential exposure levels of greenness [Normalized Vegetation Index (NDVI) in buffer of 500 m] and ambient pollutants [including particulate matter (PM) with a diameter smaller than 1 micrometres (PM₁), PM with a diameter smaller than 2.5 micrometres (PM_2.5), PM with a diameter smaller than 10 micrometres (PM₁₀) and nitrogen dioxide (NO₂)] for each participant were determined based on their home address. We used directed acyclic graph based linear mixed effect models to evaluate the comprehensive associations of residential greenness, ambient pollutants with the four cardiovascular biomarkers. Interactive effects between greenness and ambient pollutants were also estimated.
Results: Mean age of the 5,085 participants at baseline was 59.0 years, and 2,772 (54.5%) were female. Residential greenness decreased levels of cardiovascular biomarkers, while ambient pollutants increased the biomarkers. In the multivariate analyses, the changes [β (95% CIs)] of TyG index, TG/HDL-c, TC/HDL and non-HDL-c were -0.021 (-0.036, 0.007), -0.120 (-0.175, -0.066), -0.092 (-0.122, -0.062) and -0.166 (-0.666, 0.334) for every 0.1 increase in NDVI, and were 0.004 (0.003, 0.005), 0.014 (0.014, 0.019), 0.009 (0.006, 0.011) and 0.067 (-0.019, 0.154) for every 1 μg/m³ increase in PM₁. There were significant interactive effects of NDVI with air pollutants (PM₁, PM_2.5, PM₁₀, NO₂) on TyG, TG/HDL-c and TC/HDL.
Conclusion: Individuals living in areas that with lower greenness and higher levels of ambient pollutants were observed associated with increased risks of cardiovascular disease. Further research remain needed to understand the interactive effects between greenness and ambient pollutants.

Greenness; Air Pollution; Interaction Effects; Cardiovascular Risk