RESUMO
Objective To study the distribution of waist circumference (WC) in a representative group of Chinese children for establishing the Chinese WC cut-off points. Methods Cross-sectional data obtained from 15 mainland provinces and Hong Kong were collected. There were 178 865 children and adolescents, aged 7-18 years-old in total. All subjects were divided into five regional groups- costal city, non-coastal city, northern rural, southern rural, and Hong Kong, for analyzing the distribution of WC. Results Large variations in WC distribution were found among the five groups for both sexes. The coastal city group had the highest P85 WC values consistently from the early school age to 18-year-old, when comparing with other groups. In contrast, southern rural group had P85 values consistently lagged behind, in both city group and in the north rural group. Hong Kong group had a high P85 WC at early ages, but because of the smaller increments of WC during adolescence, the P85 curve was gradually exceeded by the northern rural groups. Catch-up trend was found in the two rural groups since peak puberty. These disparities were caused not only by factors related to socioeconomic and urban-rural but also to the geographic differences between the noah and the south. Because of the regional variation of WC, a "gradient" prevalence of central obesity was prospected among these groups. Closed associations were found between WC and height, weight and BMI in all age period. Comparison on the WC distributions between people from China, U.S.A or the Netherlands demonstrated the necessity of setting up China's own WC cutoffs.Sex and age-specific percentiles were obtained and smoothed by using the LMS method.Conclusion Data obtained from this study could be used to develop the national WC cutoff points for Chinese children and adolescents.
RESUMO
Objective To explore the optimal threshold values of waist circumference (WC) in detecting the risk on cardiovascular (CV) among the Chinese children and adolescents. Methods Association of WC and CV risk factors were studied among 65 898 children and adolescents aged 7-18 years whose data were pooled from nine studies carried out in China. Receive-operating characteristic analysis (ROC) and logistic regression were employed to derive optimal age- and sex-specific waist circumference references for predicting the CV risk factors. Results A slight increasing trend of CV risk factors was observed starting from the 75th percentile of waist circumference in the study population, while a remarkable increasing trend occurred from the 90th percentile. The optimal waist circumference thresholds for predicting high blood pressures were at the 75th percentile for both boys and girls, and at the 90th percentiles it could detect at least two of the above three CV risk factors. In comparison with children whose waist circumference was below the 75th percentile, the odds ratio of two CV risk factors doubled among children with waist circumference between 75th and 90th percentile, and increased by 6 times among children with waist circumference above the 90th percentile. The trend of high blood pressure increasing remained significant with waist circumference after having been stratified by BMI category. Conclusion The 75th and the 90th percentile of WC appeared to be the optimal cut-off points for predicting an increased and a substantially increased risk of CV factors in Chinese children and adolescents.