Interactive effects of green-space exposure and air pollution on cardiovascular disease risk: a study based on the CHARLS and CLHLS databases

Cardiovascular diseases are common in aging populations and are closely associated with multiple factors. However, the cumulative effects of green-space exposure and air pollutants on cardiovascular disease have not been adequately investigated. This study used CHARLS 2015 data and CLHLS 2014 data. Green-space exposure was quantified using the normalized difference vegetation index (NDVI), while exposures to PM2.5, NO2 and SO2 were assessed using the China High-resolution Air Pollutant dataset (CHAP). A composite cardiometabolic risk score was derived from five metabolic syndrome (MetS) diagnostic components: abdominal obesity, hypertension, hyperglycemia, hypertriglyceridemia, and low high-density lipoprotein. Generalized linear models (GLMs) were applied to evaluate the effects of green-space exposure and air pollutants on cardiovascular disease risk; single-, two-, and three-pollutant models were fitted, and interaction and sensitivity analyses were conducted to assess the robustness of the findings. Green-space exposure was associated with a lower risk of cardiovascular disease (OR = 0.867, 95% CI: 0.796–0.944, P = 0.001), while exposures to PM2.5, NO2, and SO2 were all linked to an increased risk. Among these pollutants, NO2 showed the strongest association, with each interquartile range (IQR) increase corresponding to a 25.9% higher risk of cardiovascular disease (OR = 1.259, 95% CI: 1.152–1.377, P < 0.001). Interaction analysis revealed that higher green-space exposure had a more pronounced protective effect under low levels of air pollution. However, under high pollution levels, greater green-space exposure appeared to amplify the adverse effects of pollutants on cardiovascular disease risk. In the multi-pollutant model, after further adjusting for three pollutants, the association between PM2.5 (OR = 1.179, 95% CI: 1.017–1.366, P = 0.028) and NO2 (OR = 1.165, 95% CI: 1.012–1.341, P = 0.034) and cardiovascular disease risk remained significant. Evidence indicates that green-space exposure confers protection for cardiovascular health, but this effect is significantly modulated by ambient air pollution.