Waist-to-height ratio as a measure of abdominal obesity in southern Chinese and European children and adolescents

BACKGROUND: Waist-to-height ratio (WHtR), with a 0.5 threshold ([WHtR.sub.0.5]), is regarded as a simple age- and gender-independent criterion of abdominal obesity (AO) and a better predictor than the 90th percentile of waist circumference ([WC.sub.P90]). OBJECTIVE: An analysis of gender and ethnic differences of WHtR and other AO indices between children and adolescents from southern China (HK: Hong-Kong, China) and Europe (LD: Lodz, Poland). SUBJECTS: Two large cross-sectional surveys of children and adolescents aged 7-19 years, one from LD (13 172) and one from HK (14 566). METHODS: The percentile and standardized values of WHtR and other parameters (WC, body mass index (BMI)) were assessed using the LMS method. The WHtR values corresponding to [WC.sub.P90] and to the BMI definition of global obesity ([BMI.sub.P95]) were evaluated with the polynomial regression model. The compliance of the AO prevalence data, obtained with two criteria ([WC.sub.P90] vs [WHtR.sub.0.5]) was analyzed using Cohen's kappa index (κC). RESULTS: The WHtR data of Polish subjects were generally higher than those of their HK peers, and the ethic differences increased with age. The WHtR values of HK boys showed a stronger relationship with BMI z-score. WHtR corresponding to [WC.sub.P90] assumed values < 0.5. An application of Cohen's kappa coefficient (κC) to Polish subjects showed either 'substantial' (κC >0.6) or 'almost perfect' (κC >0.8) agreement in the AO prevalence for both criteria ([WC.sub.P90] and [WHtR.sub.0.5]). For these criteria, either 'fair' (κC < 0.4) or 'moderate' (κC < 0.6) AO consistency ratings were observed among HK girls. In HK boys, a significant difference in the prevalence of AO was observed, independent of the criterion used. CONCLUSIONS: Our results provide further evidence of the need for developing ethnic-specific WC charts and for recommending that a WHtR cutoff of 0.5 may not be appropriate to predict cardiometabolic risk in children of different ethnic groups. International Journal of Obesity (2016) 40, 1109-1118; doi: 10.1038/ijo.2015.251