Waist circumference as a screening tool for the identification of adolescents with the metabolic syndrome phenotype

Objectives. Most published definitions of the metabolic syndrome (MetS) in children and adolescents include increased waist circumference (WC) in their criteria. To assess the clinical relevance of WC in identifying adolescents with the MetS phenotype and adverse fitness patterns, we divided a cohort of 15-year-old schoolchildren in quartiles for WC, and compared the subjects of the extreme quartiles for the presence of cardiovascular (CVD) risk factors, their clustering, insulin resistance and body fitness. Population and methods. From the original cohort of 635 adolescents investigated for childhood CVD risk, anthropometric parameters, blood pressure, fitness indexes, and serum fasting glucose, insulin and lipids were analyzed in 105 adolescents of the highest (>= 75th percentile) and 102 of the lowest (<= 25th percentile) WC quartile. Results. Adolescents with WC >= 75th percentile presented with significantly higher fasting insulin (17 +/- 0.9 vs. 9.1 +/- 1.0 mu IU/mL), triglycerides (78.0 +/- 3.4 vs. 62.3 +/- 3.3 mg/dL), LDL-cholesterol (106.8 +/- 2.8 vs. 96.1 +/- 2.8 mg/dL), homeostasis model assessment index (HOMA-IR) (3.29 +/- 1.8 vs. 1.81 +/- 0.2), systolic blood pressure (125.6 +/- 1.1 vs. 116.0 +/- 1.1 mm Hg), and diastolic blood pressure (78.0 +/- 0.9 vs. 71.5 +/- 0.9 mm Hg) and significantly lower HDL-cholesterol (46.2 +/- 1.2 vs. 53.4 +/- 1.1 mg/dL) and physical fitness as compared with their peers with WC <= 25th percentile. Clustering of three CVD factors pointing to a full MetS phenotype was found for 13.5% of the 15 year olds with WC > 75th percentile. Conclusions. Our findings suggest that WC >= 75th percentile is associated with the MetS phenotype and reduced activity in adolescence, and confirm the clinical relevance of WC as a tool for the identification of adolescents with increased CVD risk.