The Influence Of Urbanization On Overweight And Obesity Of Children And Adolescents

BackgroundChina has been experiencing rapid urbanization in recent decades. People have access to better health services, information and education. However, the rapid environmental, economic and social changes along with urbanization increase the prevalence of childhood overweight and obesity and many chronic diseases. The studies on the impacts of urbanization on childhood overweight and obesity are limited, most of which define urbanization only as population size and population density. Many important urbanized characteristics have not been considered. Thus we utilize an urbanization index to examine the association of community urbanization with overweight and obesity for children and adolescents.ObjectivesTo examine the secular trend in overweight and obesity of children and adolescents aged 7-17 in different urbanization level communities. To investigate the difference of the influence factors of child and adolescent overweight obesity in different urbanization level communities. To examine the impacts of different urbanization levels and different changes of urbanization on overweight/obesity among children and adolescents.MethodsThe samples were collected from "China Health and Nutrition Survey" which included children and adolescents aged 7～17 years (n=7014) between 1991 and 2011. We divided community urbanization index into low, middle and high levels to examine the secular trends in BMI overweight and obesity and the influencing factors of overweight and obesity among children and adolescents aged 7-17 in different urbanization level communities. Because the physical activity and leisure sedentary time measures were collected from 1997. So the study containing physical activity and leisure sedentary time utilized children and adolescents aged 7-17 years (n=4340) between 1997 and 2011. We used multilevel mixed-effect regression analysis to investigate the impacts of different urbanization levels and different changes of urbanization on overweight/obesity among children and adolescents.Results1. The urbanization index scores of different urbanization level communities increased significantly from 1991 to 2011. The urbanization index scores of high, middle and low urbanization level communities increased more than 20 points from 65.2^ 45.9 and 28.3 in 1991 to 93.5、75.2 and 48.5 in 2011 respectively.2. The mean BMI and the prevalence of overweight and obesity for children and adolescents aged 7 to 17 increased significantly from 1991 to 2011. The mean BMI for boys and girls increased from 17.2 kg/m2 and 17.4 kg/m2 in 1991 to 18.2 kg/m2 and 17.7 kg/m2 in 2011 respectively. The prevalence of overweight increased from 3.3%for boys and 3.9%for girls in 1991 to 11.0% for boys and 5.5% for girls in 2011. The prevalence of obesity increased from 1.9% for boys and 1.7% for girls in 1991 to 8.9% for boys and 7.0% for girls in 2011. The variation was different in different gender, age group and different areas. In the same survey year, children with higher parental education, parental weight status, household income and children who lived in the north part of China had higher mean BMI and were more likely to be overweight or obesity.3. From 1991 to 2011, the mean BMI and the prevalence of overweight and obesity for both boys and girls increased significantly with the increase of urbanization levels, among which the prevalence of overweight and obesity of boys who lived in the middle urbanization level community had the largest increase from 2.0% and 1.3% in 1991 to both 12.3% in 2011. Compared with children who lived in the low urbanization level communities, those who lived in the high urbanization level communities had higher mean BMI and the prevalence of overweight and obesity.4. When comparing the difference of factors affecting the overweight and obesity of children and adolescents, we found that with the improvement of community level of urbanization in the same survey year, the intakes of rice products and potato, and vegetables intake declined significantly. While the intakes of fruits, livestock and poultry meat and aquatic products, eggs, and milk showed increased trend. Children and adolescents who lived in the high urbanization level community had highest physical activity and the longest sedentary time. Children and adolescents who lived in the high urbanization level communities had higher family income, and the largest proportion of whose parents had high level education and were overweight or obesity.5. In the multilevel mixed-effect linear regression analysis, the BMI values of boys who lived in the high urbanization level community were 0.61 kg/m2 (95%CI:0.03～1.19, P<0.05) higher than those who lived in the low urbanization level community after adjustment for all potential confounders. There was no association of urbanization with BMI values in the girls. In the multilevel mixed-effect logistic regression analysis, there were no association of urbanization with the prevalence of overweight/obesity in both boys and girls after adjustment for all potential confounders.ConclusionIn this study, we found that the mean BMI of boys was higher than those who lived in the low urbanization level communities. There was no association of urbanization with BMI values in the girls and with the prevalence of overweight/obesity in both boys and girls. It is probably because community urbanization did not directly but indirectly affect children’s overweight and obesity through changing life style and family factors of children and adolescents. Also maybe the sample size in this study is limited so that we did not find the association of urbanization with the prevalence of overweight/obesity in both boys and girls.