First reference curves of waist circumference and waist-to-height ratio for Tunisian children

Abdominal obesity for children: Waist circumference (WC) and waist-to-height ratio (WTHR) reference curves are used to assess the risk of cardiovascular disease in children. The aim of this study was to develop age- and sex-smoothed WC and WTHR reference curves for Tunisian children. Data were collected during the period 2014–2015 in a cross-sectional study including 2308 children aged 6–18 years. The percentiles of WC and WTHR were developed using the LMS method. The optimal percentiles, which are associated with the body mass index (BMI) according to International Obesity Task Force (IOTF) criteria to identify overweight/obesity and with the 0.5 boundary value of WTHR to estimate cardiovascular risk, were identified by ROC curves and the Youden index (j). The results show the smoothed percentiles of WC and WTHR reference curves for Tunisian children. A comparison of the 50th percentiles with other references showed different trends in WC values. The 75th percentiles of WC and WTHR are the optimal percentiles that correspond to both PBMI25 (the percentile linked to BMI ≥ 25) and the 0.5 boundary value. However, the 90th percentiles correspond to PBMI30 (the percentile linked to BMI ≥ 30) in boys and girls. Conclusion: The new WC and WTHR reference curves can be added to clinical tools to help specialists in pediatric and physical health to reduce cardiovascular risk in Tunisian children.