title: Predictive ability of waist-to-height in relation to adiposity in children is not improved with age and sex-specific values.
abstract: A waist-to-height ratio (WHtR) ≥0.5 indicates increased health risk in children and adults. However, because of residual correlation between WHtR and height in children, dividing waist circumference by height to the power of one may be insufficient to correctly adjust for height during growth. This study aimed to determine whether age and sex-specific exponents which properly adjust for height affect the predictive ability of WHtR to correctly discriminate between children with differing fat distribution. Total and regional body fat was measured by dual-energy X-ray absorptiometry (DXA) in 778 (49% male) children and adolescents. WHtR was calculated as waist/height(1) (WHtR(a)), and using two published age and sex-specific exponents for height (WHtR(b)) (1) (WHtR(c)) (2), and compared with various DXA indexes of body composition using receiver operating curve analysis. 15% of males and 17% of females had a WHtR(a) ≥0.5, with corresponding figures of 8% and 27% for WHtR(b), and 23% and 17% for WHtR(c). WHtR(a) was significantly different from WHtR(b) (males only, P < 0.001) but not WHtR(c) (P = 0.121). Areas under the receiver operating curve (AUC) for WHtR(a) were significantly higher than AUCs for WHtR(b) or WHtR(c) in relation to DXA-measured body composition (AUCs ≥0.89 for WHtR(a) compared with AUCs of 0.71-0.84 for WHtR(b) and WHtR(c)). Simply dividing waist circumference by height (WHtR(a)) correctly discriminates between children and adolescents with low and high levels of total and central fat at least 90% of the time. Keeping your waist circumference to less than half your height provides an effective screening index of body composition during growth.
authors.affiliation: Department of Medical and Surgical Sciences, University of Otago, DSM, Dunedin, South Island, New Zealand. rachael.taylor@otago.ac.nz
authors.forename: Rachael W
authors.initials: RW
authors.lastname: Taylor
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Williams
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Grant
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Taylor
authors.forename: Ailsa
authors.initials: A
authors.lastname: Goulding
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D017677:Age Distribution; D019540:Area Under Curve; D050218:Body Fat Distribution; D001827:Body Height; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000517:prevention & control; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009520:New Zealand / Q000453:epidemiology; D009765:Obesity / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000517:prevention & control; D011237:Predictive Value of Tests; D011634:Public Health; D012372:ROC Curve; D017678:Sex Distribution; D055105:Waist Circumference