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 (ß: -0.11, 95% confidence interval[CI]: -0.13,-0.09) and waist circumference (ß: -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.

Predicting Metabolic Syndrome Using Anthropometric Indices among Chinese Adolescents with Different Nutritional Status: A Multicenter Cross-sectional Study.

OBJECTIVE: To evaluate the predictive performance of anthropometric indices for metabolic syndrome (MetS) among Chinese adolescents with different nutritional status. METHODS: We recruited 9,513 adolescents aged 10-18 years from seven provinces in China during September 2014. Anthropometric indices and blood pressure were measured at recruitment, and blood samples were collected for determining fasting plasma glucose and lipid profile. Receiver operating characteristic (ROC) analyses were used to assess the predictive performance of anthropometric indices, including body mass index (BMI) percentile, waist circumference percentile, waist-height ratio, and waist-hip ratio. RESULTS: Overall, the four anthropometric indices showed good accuracy for predicting MetS with areas under ROC curves (AUCs) ranging from 0.86 to 0.94; similar AUCs ranging from 0.73 to 0.99 were observed for participants with normal weight. The performance of all four indices was poor in overweight and obese participants, with AUCs ranging from 0.66 to 0.77 and from 0.60 to 0.67, respectively. Waist circumference showed relatively better performance in all the subgroup analyses. CONCLUSIONS: We suggest using anthropometric indices with the cutoff values presented here for predicting MetS in the overall and normal-weight adolescent population, but not in the overweight and obese adolescent population where more specific screening tests are required.

Long-term exposure to ambient air pollution and metabolic syndrome in children and adolescents: A national cross-sectional study in China.

BACKGROUND: The prevalence of metabolic syndrome (MetS) rapidly increased over the past decades. However, little evidence exists about the effects of long-term exposure to ambient air pollution on MetS in children and adolescents. OBJECTIVE: This study aims to assess the association between long-term ambient air pollution and the prevalence of MetS in a large population of Chinese children and adolescents. METHODS: In 2013, a total of 9,897 children and adolescents aged 10 to 18 years were recruited from seven provinces/municipalities in China. MetS was defined based on the recommendation by the International Diabetes Federation (IDF). Satellite based spatio-temporal models were used to estimate exposure to ambient air pollution (including particles with diameters ≤1.0 µm (PM1), ≤2.5 µm (PM2.5), and ≤10 µm (PM10), and nitrogen dioxide (NO2)). Individual exposure was calculated according to 94 schools addresses. After adjustment for a range of covariates, generalized linear mixed-effects models were utilized to evaluate the associations between air pollutants and the prevalence of MetS and its components. In addition, several stratified analyses were examined according to sex, weight status, outdoor physical activity time, and sugar-sweetened beverages (SSBs) intake. RESULTS: The prevalence of MetS was 2.8%. The odds ratio of MetS associated with a 10 µg/m3 increase in PM1, PM2.5, PM10 and NO2 was 1.20 (95%CI: 0.99, 1.46), 1.31 (95%CI: 1.05, 1.64), 1.32 (95%CI: 1.08, 1.62), and 1.33 (95%CI: 1.03, 1.72), respectively. Regarding the MetS components, we observed associations between all pollutants and abdominal obesity. In addition, long-term PM1 and NO2 exposures were associated with the prevalence of elevated fasting blood glucose. Stratified analyses detected that the associations between air pollutants and the prevalence of MetS were stronger in boys (Pinteraction < 0.05). CONCLUSIONS: We found that long-term exposure to PM2.5, PM10, and NO2 were positively associated with the prevalence of MetS in children and adolescents. Our findings may have certain public health implications for some comprehensive strategy of environment improvement and lifestyles changes in order to reduce the burden of non-communicable disease.