Greenness surrounding schools and adiposity in children and adolescents: Findings from a national population-based study in China

Background: Previous studies have indicated that exposure to green space may benefit human health. However, the available evidence concerning the effects of greenness, especially school-based greenness, on pediatric obesity is scarce. Objective: To explore the association between school-based greenness and adiposity in children and adolescents in China. Method: We conducted a nationwide cross-sectional study of 56,620 children and adolescents (aged 6–18 years) in seven provinces/municipalities across China. School-based greenness was assessed using satellite-derived Normalized Difference Vegetation Index (NDVI) and Soil Adjusted Vegetation Index (SAVI) within 100-, 500-, and 1000-m circular buffers around each school's address. Generalized linear mixed regression models were used to estimate associations of greenness with BMI z-scores (zBMI), waist circumference, and prevalent overweight/obesity. We also explored the potential mediating role of ambient air pollution and physical activity in the greenness-adiposity associations. Result: In the adjusted model, an IQR increase in NDVI_-1000m was associated with lower zBMI (β: -0.11, 95% confidence interval[CI]: -0.13,-0.09) and waist circumference (β: -0.64, 95%CI: -0.78,-0.50). Consistently, an IQR increase in NDVI_-100m, NDVI_-500m, NDVI_-1000m was associated with 7–20% lower odds of overweight/obesity in the adjusted models. Air pollutants mediated 6.5–29.1% of the association between greenness and zBMI. No significant mediation effect was observed for physical activity. Conclusion: Higher school-based greenness levels were associated with lower zBMI, waist circumference, and lower odds of overweight and obesity in children and adolescents. Ambient air pollutants may partially mediate the greenness-adiposity associations.