International Waist Circumference Percentile Cutoffs for Central Obesity in Children and Adolescents Aged 6 to 18 Years.

CONTEXT: No universal waist circumference (WC) percentile cutoffs used have been proposed for screening central obesity in children and adolescents. OBJECTIVE: To develop international WC percentile cutoffs for children and adolescents with normal weight based on data from 8 countries in different global regions and to 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 to 20 years from 8 countries in different regions (Bulgaria, China, Iran, Korea, Malaysia, Poland, Seychelles, and Switzerland). We calculated WC percentile cutoffs 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 cutoffs to predict cardiovascular risk using receiver operator characteristics curve analysis based on data from 3 countries that had available data (China, Iran, and Korea). We also examined which WC percentiles linked with WC cutoffs 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 cutoffs calculated in children and adolescents (6-18 years of age) with normal weight (excluding youth with obesity, overweight, or underweight) by linking the percentile with cardiovascular risk (area under the curve [AUC]: 0.69 for boys; 0.63 for girls). In addition, WC percentile among normal weight children linked relatively well with established WC cutoffs for central obesity in adults (eg, AUC in US adolescents: 0.71 for boys; 0.68 for girls). CONCLUSION: The international WC cutoffs developed in this study could be useful to screen central obesity in children and adolescents aged 6 to 18 years and allow direct comparison of WC distributions between populations and over time.

Establishing International Blood Pressure References Among Nonoverweight Children and Adolescents Aged 6 to 17 Years.

BACKGROUND: Several distributions of country-specific blood pressure (BP) percentiles by sex, age, and height for children and adolescents have been established worldwide. However, there are no globally unified BP references for defining elevated BP in children and adolescents, which limits international comparisons of the prevalence of pediatric elevated BP. We aimed to establish international BP references for children and adolescents by using 7 nationally representative data sets (China, India, Iran, Korea, Poland, Tunisia, and the United States). METHODS AND RESULTS: Data on BP for 52 636 nonoverweight children and adolescents aged 6 to 19 years were obtained from 7 large nationally representative cross-sectional surveys in China, India, Iran, Korea, Poland, Tunisia, and the United States. BP values were obtained with certified mercury sphygmomanometers in all 7 countries by using standard procedures for BP measurement. Smoothed BP percentiles (50th, 90th, 95th, and 99th) by age and height were estimated by using the Generalized Additive Model for Location Scale and Shape model. BP values were similar between males and females until the age of 13 years and were higher in males than females thereafter. In comparison with the BP levels of the 90th and 95th percentiles of the US Fourth Report at median height, systolic BP of the corresponding percentiles of these international references was lower, whereas diastolic BP was similar. CONCLUSIONS: These international BP references will be a useful tool for international comparison of the prevalence of elevated BP in children and adolescents and may help to identify hypertensive youths in diverse populations.

Circulating proinflammatory peptides related to abdominal adiposity and cardiometabolic risk factors in healthy prepubertal children.

OBJECTIVES: To analyze the circulating levels of proinflammatory peptides in healthy prepubertal children in relation to abdominal obesity, measured by waist circumference (WC), and to investigate their interactions with cardiometabolic risk factors. DESIGN AND METHODS: A cross-sectional study of 137 healthy prepubertal children with a mean age of 8.0±0.1 years divided into three groups according to their WC as a measure of abdominal obesity: 'normal-WC' children (25th-75th percentile, n=48), 'children at risk' (75th-90th percentile, n=39), and 'abdominally obese' (≥90th percentile, n=50) children. Auxological measurements and blood pressure (BP) were taken. Fasting levels of high-sensitivity C-reactive protein (hsCRP), interleukin 6 (IL6), tumor necrosis factor-α (TNF-α), glucose, insulin, and lipid profile were measured. Insulin resistance (IR) was assessed by homeostasis model assessment of IR (HOMA-IR). RESULTS: Abdominally obese children had significantly higher BP, insulin, HOMA-IR, total cholesterol and triglycerides (TG) compared with their normal-WC counterparts (P<0.05). HsCRP concentrations increased proportionally with the degree of abdominal obesity (r=0.443, P<0.0001), whereas IL6 and TNF-α were not significantly associated with any of the adiposity variables. After controlling for adiposity, hsCRP was significantly correlated with systolic BP (r=0.257, P=0.004), TNF-α levels were related to high-density lipoprotein cholesterol (HDL-C; r=-0.216, P=0.016) and TG (r=0.196, P=0.029), whereas the relationship between IL6 and HDL-C reduced its magnitude to an insignificant level (r=-0.173, P=0.055). CONCLUSIONS: Healthy prepubertal children with abdominal obesity have associated inflammatory and cardiometabolic alterations, interacting with each other.

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.