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Title: Cardiometabolic risk assessments by body mass index z-score or waist-to-height ratio in a multiethnic sample of sixth-graders

Author
item KAHN, HENRY - Centers For Disease Control And Prevention (CDC) - United States
item EL GHORMLI, LAURE - George Washington University
item JAGO, RUSSELL - University Of Bristol
item FOSTER, GARY - Temple University
item MCMURRAY, ROBERT - University Of North Carolina
item BUSE, JOHN - University Of North Carolina
item STADLER, DIANE - Oregon Health & Science University
item TREVINO, ROBERTO - Social & Health Research Center
item BARANOWSKI, TOM - Children'S Nutrition Research Center (CNRC)

Submitted to: Journal of Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2014
Publication Date: 7/1/2014
Citation: Kahn, H.S., El ghormli, L., Jago, R., Foster, G.D., McMurray, R.G., Buse, J.B., Stadler, D.D., Trevino, R.P., Baranowski, T. 2014. Cardiometabolic risk assessments by body mass index z-score or waist-to-height ratio in a multiethnic sample of sixth-graders. Journal of Obesity. 2014:421658.

Interpretive Summary: Calculating body mass index z-score (BMIz) requires access to normative growth charts. This can be challenging for the clinician and is limited by the reference group used to establish the norms. Waist-to-height ratio (WHtR) may provide information similar to BMIz and not require normative growth charts. This study compared BMIz and WHtR in predicting several cardiometabolic risk factors. The correlations tended to be similar even within groups separated by gender, ethnicity, and level of fatness. WHtR may provide an important clinically useful substitute for BMIz among children.

Technical Abstract: Convention defines pediatric adiposity by the body mass index z-score (BMIz) referenced to normative growth charts. Waist-to-height ratio (WHtR) does not depend on sex-and-age references. In the HEALTHY Study enrollment sample, we compared BMIz with WHtR for ability to identify adverse cardiometabolic risk. Among 5,482 sixth-grade students from 42 middle schools, we estimated explanatory variations (R2) and standardized beta coefficients of BMIz or WHtR for cardiometabolic risk factors: insulin resistance (HOMA-IR), lipids, blood pressures, and glucose. For each risk outcome variable,we prepared adjusted regression models for four subpopulations stratified by sex and high versus lower fatness. For HOMA-IR, R2 attributed to BMIz or WHtR was 19%–28% among high-fatness and 8%–13% among lower-fatness students. R2 for lipid variables was 4%–9% among high-fatness and 2%–7% among lower-fatness students. In the lower-fatness subpopulations, the standardized coefficients for total cholesterol/HDL cholesterol and triglycerides tended to be weaker for BMIz (0.13–0.20) than for WHtR (0.17–0.28). Among high-fatness students, BMIz and WHtR correlated with blood pressures for Hispanics and whites, but not black boys (systolic) or girls (systolic and diastolic). In 11-12 year olds, assessments by WHtR can provide cardiometabolic risk estimates similar to conventional BMIz without requiring reference to a normative growth chart.