Association between residential greenness and diabesity among adults in southwestern China: The role of physical activity and ambient air pollutants.

BACKGROUND

While green space exposure has been associated with reduced risks of diabetes and obesity separately, its relationship with diabesity remains unclear. This large-scale cross-sectional study examined the relationship between residential greenness and diabesity among 76,545 adults from the China Multi-Ethnic Cohort, while assessing potential mediation by air pollution (PM₁, PM, PM₁₀, NO₂) and physical activity (PA).

METHODS

Residential greenness was assessed using satellite-derived Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) within 250 m, 500 m, and 1000 m buffers. Diabesity was defined as coexisting diabetes (fasting glucose ≥126 mg/dL or HbA1c ≥6.5 %) and obesity (BMI ≥28 kg/m²). Mediation and interaction analyses evaluated the roles of PA and air pollutants (PM₁, PM, PM₁₀, and NO₂).

RESULTS

Logistic regression models adjusted for sociodemographic, lifestyle, and environmental covariates revealed that higher residential greenness (per IQR increase in NDVI-500m and EVI-500m) was associated with 23 % (OR = 0.77, 95 % CI: 0.71-0.85) and 21 % (OR = 0.79, 95 % CI: 0.73-0.87) lower diabesity risk, respectively. Notably, stronger protective effects were observed among minorities, rural residents, and less-educated individuals. Mediation analysis indicated that PM, PM₁₀, and PA accounted for 16-52 % of the protective effect. While significant antagonistic interactions between greenness and air pollutants were detected (all P < 0.001), no interaction was observed with PA.

CONCLUSIONS

These findings suggest that residential greenness is inversely associated with diabesity risk, partially mediated by reduced air pollution and increased PA. Targeted green space interventions may mitigate diabesity, particularly in vulnerable subgroups.