Association of long-term exposure to green space with cardiovascular health and the mediating role of triglyceride-glucose in dex in middle-aged and older Chinese adults: a nationwide cohort study

Few studies have investigated the associations between green space, the triglyceride-glucose (TyG) index, and cardiovascular health outcomes. This study aims to examine the relationships between green space and chronic cardiovascular diseases among middle-aged and older Chinese adults, while also evaluating the potential mediating effect of the TyG index.

Baseline and follow-up data were collected from the 2011 and 2015 waves, respectively, of the China Health and Retirement Longitudinal Study (CHARLS). Inverse probability of treatment weighting was used to address selection bias. City-level cluster-robust logistic regression analysis was used to assess associations between green space (2011–2014) and hypertension, heart disease, and dyslipidemia. Counterfactual exploratory mediation analysis examined the mediating role of the TyG index. Restricted cubic splines were used to explore the dose-response relationships between green space and the outcomes.

Among 11,925 participants, each 1 standard deviation (0.0922) increment in the Normalized Difference Vegetation Index (NDVI) was associated with a 13% lower risk of hypertension (OR = 0.87, 95% CI: 0.83–0.92, P < 0.001), with a linear dose-response relationship. No significant independent associations were observed for heart disease (OR = 0.92, 95% CI: 0.82–1.03, P = 0.142) or dyslipidemia (OR = 0.96, 95% CI: 0.86–1.06, P = 0.406). Mediation analysis showed that the TyG index partially mediated the NDVI-hypertension association (indirect effect P < 0.05), the proportion mediated was 2.9% (95% CI: 1.9%–4.1%).

Long-term residential green space exposure is significantly associated with a lower risk of hypertension in middle-aged and older Chinese adults, with the TyG index playing a modest partial mediating role. No significant independent associations were observed for heart disease or dyslipidemia. Enhancing urban greening may be an effective environmental strategy for the primary prevention of hypertension.