Background: This study investigates the concordance of four waist circumference (WC) measurement sites, and examines their relationships with nutritional status and cardiometabolic risk.
Subjects and methods: In 91 females / 89 males (6.1-19.9 years; 12.2% overweight), WC was assessed beneath the lowest rib (WCR), 4 cm above the umbilicus (WC4), above the iliac crest (WCC), and midway between WCR/WCC (WCM). 'Overwaist' was defined as a WC > 90th age-/sex-specific percentile. Pubertal stage was assessed according to Tanner. Body composition (air-displacement plethysmography), blood pressure, lipid profile, glucose/insulin levels, and HOMA-IR (homeostasis model assessment of insulin resistance) were measured.
Results: Medians of WCs (cm) for females/males were WCR (64.4/69.5) < WC4 (64.6/70.2) < WCM (67.1/71.2) < WCC (71.5/ 74.2). Although closely related to each other (all r > 0.93; p < 0.001), paired comparisons revealed differences between WCs in their magnitudes which was stronger for females than males. Prevalence of 'overwaist' differed according to measurement site in females/males: WCR (13.2/15.7%) < WC4 (14.3/ 19.1%) < WCM (18.7/22.5%) < WCC (37.4/30.3%). After adjusting for age and pubertal status, WCs were closely related to body mass index (BMI) (all r > 0.86; p < 0.001), percent fat mass (%FM; all r > 0.61; p < 0.001), and comparably associated with cardiometabolic risk factors. However, stronger correlations were found for i) WCR vs. WC4 with BMI in males (r = 0.93 vs. 0.91; p < 0.05), ii) WCC vs. WC4 with %FM in females (r = 0.67 vs. 0.61; p < 0.05), iii) WCC vs. WCR with triglycerides in females (r = 0.29 vs. r = 0.22; p < 0.05), and iv) WCC (r = 0.36) vs. other WCs (r = 0.30-0.32) with low-density lipoprotein cholesterol (LDL-C) in males (p < 0.05).
Conclusion: WCs measured at different sites were closely correlated with BMI and %FM as well as comparably associated with cardiometabolic risk factors. However, different WCs had different magnitudes, which was more obvious in females and led to discordant results with respect to 'overwaist' and risk assessment.