Appropriate neck circumference and waist-to-height ratio cut-off points as predictors of obesity and cardiovascular risk in adolescents

ABSTRACT OBJECTIVE To determine neck circumference (NC) and waist-to-height ratio (WHtR) cut-off points as predictors of obesity and cardiovascular risk in adolescents. METHODS Cross-sectional study developed with a subsample of 634 adolescents aged 18 and 19 years belonging to the third phase of the “RPS” cohort (Ribeirão Preto, Pelotas and São Luís) carried out in 2016. The area under the ROC curve (AUC) was identified to assess the predictive capacity of NC and WHtR in relation to the percentage of body fat (�), obtained by air displacement plethysmography (ADP), and the cardiovascular risk estimated by the Pathobiological Determinants of Atherosclerosis in Youth (PDAY). RESULTS The prevalence of obesity by � was 7.6% in males and 39.4% in females (p-value <0.001), and the high PDAY risk was 13.8% and 10.9%, respectively. For males, NC cut-off point was 44.0 cm and the AUCs were 0.70 (95%CI 0.58-0.83) to predict obesity and 0.71 (95%CI 0.62-0.80) to predict high cardiovascular risk; for females, NC cut-off point was 40 cm and the AUCs were 0.75 (95%CI 0.69-0.80) and 0.63 (95%CI 0.53-0.73), respectively. WHtR cut-off point was 0.50 for both sexes; for males, the AUCs to predict obesity and high risk according to PDAY were 0.90 (95%CI 0.80-0.99) and 0.73 (95%CI 0.63-0.82), respectively; for females, they were 0.87 (95%CI 0.83-0.90) and 0.55 (95%CI 0.45-0.65), respectively. CONCLUSION WHtR and NC are good discriminators to assess obesity and cardiovascular risk in adolescents, especially in males.

**摘要**
【研究目的】明确颈围（neck circumference, NC）与腰围身高比（waist-to-height ratio, WHtR）作为青少年肥胖及心血管风险预测指标的截断值。
【研究方法】本研究为横断面研究，纳入2016年开展的"RPS"队列（里贝朗普雷图、佩洛塔斯与圣路易斯）第三阶段的634名18~19岁青少年子样本。以空气体积描记法（air displacement plethysmography, ADP）测得的体脂百分比，以及基于青少年动脉粥样硬化病理决定因素（Pathobiological Determinants of Atherosclerosis in Youth, PDAY）量表评估的心血管风险作为结局指标，通过受试者工作特征曲线下面积（area under the ROC curve, AUC）评估NC与WHtR的预测效能。
【研究结果】按体脂百分比判定的肥胖患病率，男性为7.6%，女性为39.4%（P<0.001）；高PDAY心血管风险率分别为13.8%与10.9%。男性颈围截断值为44.0cm，其预测肥胖的AUC为0.70（95%置信区间0.58~0.83），预测高心血管风险的AUC为0.71（95%置信区间0.62~0.80）；女性颈围截断值为40cm，对应预测肥胖与高心血管风险的AUC分别为0.75（95%置信区间0.69~0.80）与0.63（95%置信区间0.53~0.73）。男女腰围身高比截断值均为0.50；男性腰围身高比预测肥胖与高PDAY风险的AUC分别为0.90（95%置信区间0.80~0.99）与0.73（95%置信区间0.63~0.82）；女性则分别为0.87（95%置信区间0.83~0.90）与0.55（95%置信区间0.45~0.65）。
【研究结论】腰围身高比与颈围可有效区分青少年的肥胖及心血管风险状态，在男性群体中尤为显著。