| Backgrounds:In the past 30 to 40 years,obesity among children and adolescents has become an increasingly urgent public health problem worldwide,especially in China in recent years.Obesity has seriously affected children and adolescents’ physical development,physical and mental health,social adaptation,fertility,labor capacity,disease burden and other aspects of social and economic developments.With the awareness increasing of the hazards of obesity in children and adolescents,the voice of prevention and intervention has gradually increased.In order to make decisions scientifically and allocate health resources rationally,it is more urgent and necessary than before to conduct in-depth researches on the distribution of obesity prevalence among children and adolescents,local characteristics,influencing factors at different levels such as individual and community,and the priorities of intervention.From community to the provincial level,obesity prevalence among children and adolescents are not distributed evenly,and the causes of obesity are complex and changeable.It is also because of the complexity and comprehensiveness of its distribution,causes,consequences and purposeful interventions,in which traditional epidemiological methods have seemed to be inadequate,that it is necessary to conduct a systematic and comprehensive study on the environmental impact factors of obesity in children and adolescents from the perspective of eco-epidemiology to provide suggestions and foundations for promoting the formation of complementary,coordinated and organized health action with high participation of all parties of concerned social organizations,including governments,international organizations,civil society organizations and corporate enterprises.Objectives:1.To explore the influencing factors of obesity among Chinese children and adolescents,which being related to not only individual food intake,physical activity,lifestyle and obesogenic environmental fators,but also wider obesogenic environmental factors from higher observational level of community or province;and to determine the specific influencing factors and their characteristics.2.To analyze the characteristics of macro-influencing factors and intervention priorities of obesity among Chinese children and adolescents.3.To analyze and predict the spatial and temporal distribution characteristics and development trends of obesity prevalence in 31 provinces(autonomous regions and municipalities)of China.4.Based on the existing survey data and analysis results,provide macro-response suggestions.5.To explore the research methods and directions of obesity in children and adolescents in China.Research contents and methods:Part 1,the multi-level mixed effect models of food environmental factors on obesity in children and adolescents were studied.Based on the food environments and physical measurement data from China Health and Nutrition Survey 2011,in which 1416 children and adolescents aged 7-17 years with relatively complete data were selected as the research objects,and combined with the provincial food environmental data from China Statistical Yearbook 2011 and other data sources,a three-level(province-community-individual)logistic random intercept mixed effect model to the binary results of being obesity or not was constructed to determine the statistical significance of stratified analysis at the provincial and community levels.The model was used to perform single-factor and multi-factor scanning and examination for the collected 10 categorical variables and 25 continuous variables successively,to analyze the influence of food environmental factors on childhood and adolescent obesity,and to determine the relevant factors and their characteristics,the priorities of the related factors and the types of modifiable factors.Part 2,based on the province-community-individual multi-level models,scanning studies of food and obesogenic environmental factors among Chinese children and adolescents were carried out.On basis of Part 1,more food and social-economic obesogenic environmental factors were included in the analysis of multi-level mixed effect model for examination and scanning,in order to find out that in addition to food environments if there are wider obesogenic environmental factors influencing obesity among children and to determined their characteristics,as well as the relationship between food environment and other obesogenic environments.Based on the data of 1416 children and adolescents aged 7-17 years old with relatively complete data of food,physical examination and community environments from the China Health and Nutrition 2011 Survey and based on the data of provincial social-economic environments from China Statistics Yearbook 2011,Food industry yearbook 2011-2013,China Health Statistics Yearbook 2011,China Education Yearbook 2011 and other sources,a two-level logistic mixed effect model was constructed finally according to results of the Wald test on statistical significance of stratified random effect analysis at the provincial and community levels.And the model was used to perform single-factor and multi-factor scanning and examination on 171 variables from 14 dimensions collected,and to explore the influence characteristics of food and obesogenic environmental factors on childhood and adolescent obesity and the priorities of the related factors.Part 3,based on the analysis of the obesogenic environmental variability and bayesian model,the spatio-temporal predictions on the obesity prevalence among Chinese children and adolescents were studied.In the previous two parts of this study,the difference and variants of obesity distribution among children and adolescents at the provincial level in China had been tested to be with statistical significance.In this part,obesity data of 4803 children and adolescents aged 7-17 years were collected from three rounds of China Health and Nutrition Survey(CHNS)in 2000(2249 in 9 provinces),2006(1138 in 9 provinces)and 2011(1416 in 12 provinces)and socio-economic obesogenic environmental data of 31 provinces in corresponding years from China Statistical Yearbooks and other sources were collected and used.Through scanning and checking these data,we selected 12 predictors and constructed the analytic model based on partial least squares regression(PLSR)and the prediction model based on Bayesian analysis.And these robust regression models constructed were used in the medical field successfully to determined variations of the priorities of obesogenic environmental factors among Chinese children and adolescents aged 7-17 years from 2000 to 2011 at provincial level.And the thematic maps of obesity prevalence among children and adolescents in 31 provinces of China in 2000,2006,2011,2015,2020 and 2030 were inferred,and suggestions for the research and intervention of obesity in children and adolescents at macro-level were provided.The data of Hong Kong,Macao and Taiwan were not included in this study.Results:1.In the first and second part of this study,the stratified random effects of the three-level logistic random intercept mixed effect model of province-community-individual were analyzed by Wald test.The results showed that there were statistically significant differences in the distribution of obesity at provincial level and stratified analysis(P<0.005,χ2=10.34),but there was no statistical significance at the community level(P>0.100,χ2=2.28 e-14),with goodness of fit(log likelihood =-410.29).2.In the first part,when food environments were the main research content,the provincial daily consumption of edible oil per capita(OR=1.183170,P<0.001,95%CI:1.100540-1.272000)and GDP per capita(OR=1.000060,P=0.001,95%CI:1.000030-1.000100)were positively correlated with obesity in children and adolescents3.In the second part,food and the wider obesogenic environments were taken as the research contents.According to the descending order of correlation(OR value),individual weight self-evaluation(OR=22.310190,P<0.001,95%CI:10.009880-49.725320),media of TV coverage(OR=1.824960,P=0.021.,95%CI:1.094720-3.042300),per capita daily edible oil consumption(OR=1.166470,P<0.001,95%CI:1.084850-1.254230),the dependency ratio of children(OR=1.151810,P=0.018.95%CI:1.024120-1.295420),transportation capacity(OR=l.000080,P=0.002,95%CI:1.000030-1.000130)were positively correlated with obesity at the age of 7-17.The appropriate location of the nearest free market in the community was negatively correlated with obesity(OR=0.588280,P=0.037,95%Cl:0.357080-0.969170).4.In the first part of the study,take the age group of 7-10 years old as the control group,the age groups of 11-14 years old and 15-17 years old were negatively correlated with obesity:the age group of 11-14 years old(OR=0.595180,P=0.049,95%CI:0.354650-0.998850)and the age group of 15-17 years old(OR=0.132250,P<0.001,95%CI:0.047160-0.370840),respectively;in the second part of the study(OR=0.383300,P<0.001,95%CI:0.238220-0.616720)and(OR=0.111610,P<0.001,95%CI:0.051480-0.241980)correspondingly.5.In the third part of the study,we found that in the three rounds of CHNS survey,the priorities of provincial obesogenic environments in China were different and variable.According to the descending order of VIP,the four most important factors of childhood and adolescent obesity were transportation capacity,school policy score,provincial GDP,and modified water source ratio in 2000;transportation capacity,provincial GDP,food industry development level and per capita consumption of vegetable in 2006;per capita consumption of edible oil,level of development of food industry,modified water source ratio and provincial GDP in 2011.In three different survey years,the seven predictors of increasing importance were:per capita consumption of edible oil,child dependency ratio,food industry development level,media(TV coverage),per hundred household washing machine ownership,maternal illiteracy rate,healthcare service level,etc.;one predictor of declining importance was transportation capacity;four predictors of lacking of a stable trend in importance were provincial GDP,per capita vegetable consumption,school policy scores and modified water availability.6.In the third part of the study,the bayesian spatio-temporal prediction model was optimized,and the deviation information criterion used for its goodness of fit was 155.60.The parameter estimations were statistically significant(P<0.05):intercept(-717.040000,95%CI:-1186.030000～-248.048000),survey year(0.358400,95%CI:0.124500-0.592400),square value of food industry level(0.000300,95%CI:0.000200-0.000400)and logarithmic value of medical service level(5.374200,95%CI:2.513800-8.234700).According to the predictive model fitted,we found the following quantitative relations.(1)The prevalence of obesity among children and adolescents increased by 0.36%annually on average from 2000 to 2011 and was more influenced by food industry development level and healthcare service level.(2)Food industry level seems to be an "Amplifier" of childhood obesity,with "1" being the critical value,which actually means when the development level of the food industry reaches or exceeds the scale of 10,000 tons of milk products per year in a province,the "Amplifier" can accelerate prevalence of obesity more quickly in the form of square of food industry level.(3)Healthcare service level seems to be a "Balancer" of childhood obesity,with "1"being the critical value,which actually means when the number of doctors per thousand persons is less than 1 or more than 1,healthcare service level shows a negative or positive effect on the nutritional status of the population in form of logarithmic relationship.From a qualitative perspective,whether healthcare practitioners focus on"disease treatment" or "nutrition and health integrity" may fundamentally determine the direction,nature and future trends of the role of healthcare in the obesity epidemic.Hence,we can term it a "Balancer."7.In the third part of the study,the overall average obesity prevalence of children and adolescents in 31 provinces of China in 2000,2006,2011,2015,2020 and 2030 is predicted to be 2.23%,5.11%,10.77%,12.20%,13,99%and 17.58%,respectively.8.The predicted maps show that obesity among children and adolescents in northern and eastern China is clustered.Conclusion:1.Through systematic analysis of eco-epidemiology,this study found that obesity among children and adolescents aged 7-17 in China was significantly affected not only by self-recognition of individual weight and age group,but also by the location of free market in community and media marketing(TV coverage),daily consumption of edible oil per capita,provincial GDP,long-term development level of food industry and medical service at provincial level,as a higher level of food and obesogenic environments.The combination of the food environment and the wider obesogenic environments are the causes of obesity.Stratified analysis at provincial level and comprehensive policy intervention across departments are of practical significance and necessity.2.In terms of the spatial and temporal distribution and development trend of obesity prevalence among children and adolescents in 31 provinces(autonomous regions and municipalities directly under the Central Government),the northern and eastern regions of China are the areas with high obesity prevalence and the key areas requiring intervention.From 2000 to 2011,the annual growth rate of obesity prevalence among children and adolescents in China was 0.36 percentage points.3.From 2000 to 2011,the priorities of several factors in the obesogenic environments at the provincial level had changed significantly.And from long-term longitudinal observation,we found that the development level of the food industry and the level of medical service played the roles of "Amplifier" and "Balancer" in the forms of particular quantitative relationships respectively,with significant impacts on the prevalence of obesity in children and adolescents.4.Under the multi-level model analysis framework,in terms of individual factors,there were two new findings:(1)The positive correlation between individual weight self-recognition degree and childhood and adolescent obesity was 10-20 times stronger than that of other positive correlation factors.(2)Pre-puberty(7-10 years old)may be a high-risk period for childhood and adolescent obesity.5.From the systemic study,the macro-control and intervention priorities for the urgent public health problem of obesity among children and adolescents in China are as following:in terms of geospatial distribution north and East are the main directions;in terms of population distribution pre-puberty(7-10 years old)should be particularly stressed;the sectors and fields mainly involved are food industry,edible oil consumption,medical and health services,publicity and education,etc.6.Under the new conditions of social and economic development,it is suggested to strengthen the whole society’s re-understanding of the relationship between food nutrition and human health through education,legislation and regulation construction,to form common will and social norms,to systematically promote the reform of the supply side of food industry and the reduction of the average consumption of edible oil in populations.We should promote the medical care,public health system and education system for young school-age children to strengthen the propaganda,education and specific guidance on food,nutrition.,health and sports and to emphasize the harmfulness of childhood obesity to children’s health and development in their lifetime.In view of the complexity of the problem,it is necessary for the whole society to work together to promote innovations in food industry,create healthier food choice and consumption environments,and build more friendly environments conduciving to physical activities. |
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