Multi-level scanning of environmental factors of body mass index of children and adolescents aged 7-17 years in China .

To investigate the influence of environmental factors on body mass index of children and adolescents in China. Using data from the China Health and Nutrition Survey, the research object to 7 - 17 years old children and adolescents who participated in 2000, 2006, 2011, and 2015 round of survey with complete data, a total of 6 626 children and adolescents (male 3 473, female 3 153) were investigated under univariate analysis for each environmental factor variable before using Partial Least Square Regression fitting a linear model for further screening. Finally, we fitted a three-level linear mixed-effects model distinct by urban and rural area for analysis. The three-level null model, log likelihood=-17 034.68, =483.06, <0.001. Intern-class correlation coefficient () showed that community-level was 9.97%, and both community and individual were 39.38%. The three-level model also showed that urban model's urbanization index (=-0.05, 95%: -0.09--0.01, <0.05), the park location (=-0.88, 95%: -1.72 - -0.04, <0.05), 15 - 17 age group (=-1.04, 95%:-1.78 - -0.30, <0.05) were negatively correlated with BMI. The distance to the gym (=0.12, 95%: 0.02 - 0.22, <0.05), the number of home TV sets (=0.50, 95%: 0.08 - 0.92, <0.05) and the frequency of parents' alarm of fiction TV program contents (=1.85, 95%: 0.70 - 3.00, <0.05) were correlated with BMI. Rural urbanization index (=-0.04, 95%:-0.07 - -0.01, <0.05). Rural per capita income (=-7.29e, 95%:-1.00e - -6.77e, <0.05), parents' restricted frequency of watching TV (=-1.29, 95%:-2.36 - -0.21, <0.05), adipo-energy ratio (=-0.03, 95%:-0.06 - -1.00e, <0.05) were negatively correlated with the BMI. Factors as the frequency of parents' alarm of fiction TV program contents (=3.01, 95%: 0.03 - 6.00, <0.05), the survey time was 2015 (=4.83, 95%: 1.96 - 7.69, <0.05) were correlated with BMI. Environmental factors could indirectly influence the change of BMI of children and adolescents to different degrees and various aspects. Urbanization index and rural per capita income had a slight protective effect on increasing BMI of children and adolescents. At the community level, attention should be paid to the setting of activity places around the living environment of children and adolescents. Family members should also guide their children and adolescents to develop nice behavior in watching TV.