Association of greenness surrounding school with aggression among adolescents: A multi-site study in China

Association of greenness surrounding school with aggression among adolescents was not well understood. This study aimed to investigate the associations of greenness surrounding school with adolescents' total and sub-types of aggression and explore potential mediators underlying these associations. A multi-site study of 15,301 adolescents aged 11-20 years were recruited through a multistage, random cluster sampling across 5 representative provinces in mainland China. Satellite-derived Normalized Difference Vegetation Index (NDVI) values within circular buffers of 100 m, 500 m, and 1000 m surrounding school were used to indicate the adolescents' greenness exposure. We used the Chinese version of Buss and Warren's Aggression Questionnaire to assess total and sub-types of aggression. Daily concentrations of PM2.5, and NO2 were obtained from the China High Air Pollutants datasets. Per IQR increment of NDVI 100 m and 500 m surrounding school was associated with lower odds of total aggression; odds ratio [OR] with 95% CI was 0.958 (0.926-0.990) for the 100 m buffer and 0.963 (0.932-0.996) for the 500 m buffer, respectively. Similar associations can be observed in two sub-types of aggression, including verbal (NDVI 100 m: 0.960 (0.925-0.995); NDVI500m: 0.964 (0.930-0.999)) and indirect aggression (NDVI 100 m: 0.956 (0.924-0.990); NDVI500m: 0.953 (0.921-0.986)). There were no sex and age differences in the associations of school surrounding greenness with aggression, except that the beneficial associations of greenness exposure with total aggression (0.933(0.895-0.975) vs.1.005(0.956-1.056)), physical aggression (0.971(0.925-1.019) vs.1.098(1.043-1.156)), and hostility (0.942(0.901-0.986) vs.1.016(0.965-1.069)) were greater among participants aged ≥16 years than those aged<16 years. PM2.5 (proportion mediated estimates: 0.21; 95% CI: 0.08, 0.94) and NO2 (-0.78, 95% CI: -3.22, -0.37) mediated the association of NDVI 500 m surrounding school with total aggression. Our data indicated that exposure to greenness in school surroundings was associated with reduced aggression, particularly in verbal and indirect aggression. The presence of PM2.5 and NO2 partially mediated these associations.