International waist circumference percentile cut-offs for central obesity in children and adolescents aged 6-18 years

Context: No universal waist circumference (WC) percentile cut-offs used have been proposed for screening central obesity in children and adolescents. Objective: To develop international WC percentile cut-offs for children and adolescents with normal weight based on data from eight countries in different regions and examine the relation with cardiovascular risk. Design and Setting: We used pooled data on WC in 113,453 children and adolescents (males, 50.2%) aged 4-20 years from eight countries in different regions (Bulgaria, China, Iran, Korea, Malaysia, Poland, Seychelles, and Switzerland). We calculated WC percentile cut-offs in samples including or excluding children with obesity, overweight or underweight. WC percentiles were generated using the general additive model for location scale and shape (GAMLSS). We also estimated the predictive power of the WC 90th percentile cut-offs to predict cardiovascular risk using receiver operator characteristics curve analysis based on data from three countries that had available data (China, Iran and Korea). We also examined which WC percentiles connected with WC cut-offs for central obesity in adults (at age of 18 years). Main Outcome Measure: WC measured based on recommendation by the World Health Organization. Results: We validated the performance of the age- and sex- specific 90th percentile WC cut-offs calculated in children and adolescents (6-18 years of age) with normal weight (excluding youth with obesity, overweight or underweight) by linking it with cardiovascular risk (AUC: 0.69 for boys; 0.63 for girls). In addition, WC percentile among normal weight children linked relatively well with established WC cut-offs for central obesity in adults (e.g., AUC in US adolescents: 0.71 for boys; 0.68 for girls). Conclusion: The international WC cut-offs developed in this study could be useful to screen central obesity in children and adolescents aged 6-18 years and allow direct comparison of WC distributions between populations and over time.