Waist circumference percentile curves for Bulgarian children and adolescents aged 6-18 years

Background. Waist circumference (WC) is a simple, easily available anthropometric measurement, giving relevant information about fat distribution and reflecting the degree of central adiposity in children. It appears to be the main risk factor for the progress of the metabolic syndrome. Our aim was to develop age- and sex-specific WC percentile curves for Bulgarian children/adolescents and to compare them with those from other countries. Methods. A representative cross-sectional study of 3 810 healthy Bulgarian children/adolescents (2 052 males) aged 6-18 years, conducted in 2006/07. Body weight, height and WC were measured and body mass index (BMI) was calculated. Sex- and age-specific WC percentile curves were constructed using the LMS method. Results. WC increased with age in both sexes (P < 0.0001), with higher values in boys at every age and percentile point. This difference became significant from age 11 years onwards (P < 0.05). The boys' values continued to increase steeply after this age, while in girls we found a constant continuing increase until the age of 15. Thereafter WC began to decrease and level off. The WC percentile values in Bulgarian children were lower than in US children, higher than in British and Turkish children, and similar to those of their Cypriot peers. Conclusions. For the first time, WC percentile curves were constructed for Bulgarian children/adolescents. A unique standardized method for WC measurement in children is needed for more acceptable international comparisons.