Primary And Middle School Students In Different Geomorphic Areas Of Yunnan Province Exploration Of BMI Screening Threshold For Overweight And Obesity

Objective(s): In order to provide theoretical and scientific basis for the measurement,prevention and control of overweight and obesity in children and adolescents in Yunnan province,the BMI threshold points of overweight and obesity in primary and middle school students aged 7 to 18 years were explored in different landform areas(dam area,semi-dam area and mountain area).Methods: The stratified random cluster sampling method was adopted to select samples from 7 cities,16 counties(districts)and 95 primary and secondary schools,with a total of 24,166 students(7024 students in dam area,7125 students in semi-dam area and 10017 students in mountainous area).The survey collected the demographic data and the basic measurement data of height and weight of primary and middle school students aged 7 ～ 18 years.BMI percentile curve and boundary point of overweight and obesity in primary and middle school students aged 7 to 18 years in different landform areas(dam area,semi-dam area and mountain area)in Yunnan province were established by using LMS method.The initial pseudothreshold value of this study was compared with the standards of WHO,NHCC and IOTF.The status quo of overweight and obesity among primary and secondary school students in Yunnan Province was analyzed.Results: In this study,the LMS method was used to fit the BMI percentile curve,and the difference between the actual value and the fitting value in each age group was-0.49 ～ 0.59,indicating a good curve fitting effect.BMI values of primary and secondary school students aged 7 ～ 18 in dam area,semi-dam area and mountainous area showed a gradual increasing trend with the increase of age,and both boys and girls entered the peak BMI growth since the age of 10.But after 14 years old,the overall BMI curve of boys increased more evenly;The increase in BMI curve of girls slows down after the age of 14.BMI threshold points were constructed by percentile method and adult threshold point connection method,and verified by NHCC standard.The results showed that the kappa values of percentile method and adult threshold point connection method were 0.912 and 0.919,respectively,and the kappa coefficients were both greater than 0.9,showing good consistency,while the kappa coefficient of threshold point method was greater than the percentage method.Compared with domestic and foreign standards,the detection rate of overweight was in descending order from the highest to the lowest by the initial preconceived threshold standard,WHO standard(11.1%),NHCC standard(9.5%)and IOTF standard(9.3%).The detection rate of obesity in descending order was NHCC standard(5.5%),WHO standard(4.7%),preliminary threshold standard of this study(3.2%)and IOTF standard(2.5%),and the difference was statistically significant(P<0.05).From the perspective of different age groups,the overweight and obesity rates of the four criteria all showed a trend of increasing first and then gradually decreasing with the increase of age,and the overweight and obesity rates peaked in the age group of 9 to 12 years old.Conclusion(s): In this study,there are significant ethnic and regional differences in BMI values.The threshold point standards for overweight and obesity of primary and secondary school students aged 7 to 18 in Yunnan Province are different from those established internationally(WHO,IOTF)and domestic(NHCC).Therefore,it is necessary to establish a threshold point for overweight and obesity BMI screening of primary and secondary school students in Yunnan Province.However,this study only conducted a preliminary exploratory study on the threshold of overweight and obesity in children and adolescents.In practice,its feasibility as a screening standard for the population needs to be further verified.In addition,the results of this study showed that the detection rates of overweight and obesity of the four criteria all reached their peak in the age group of 9-12 years old,suggesting that early adolescence is the period of the formation of overweight and obesity in children and adolescents,and also a key period for the prevention of overweight and obesity.