Is waist-to-height ratio a useful indicator of cardio-metabolic risk in 6-10-year-old children?

BACKGROUND Childhood obesity is a public health problem worldwide. Visceral obesity, particularly associated with cardio-metabolic risk, has been assessed by body mass index (BMI) and waist circumference, but both methods use sex-and age-specific percentile tables and are influenced by sexual maturity. Waist-to-height ratio (WHtR) is easier to obtain, does not involve tables and can be used to diagnose visceral obesity, even in normal-weight individuals. This study aims to compare the WHtR to the 2007 World Health Organization (WHO) reference for BMI in screening for the presence of cardio-metabolic and inflammatory risk factors in 6-10-year-old children. METHODS A cross-sectional study was undertaken with 175 subjects selected from the Reference Center for the Treatment of Children and Adolescents in Campos, Rio de Janeiro, Brazil. The subjects were classified according to the 2007 WHO standard as normal-weight (BMI z score>-1 and<1) or overweight/obese (BMI z score≥1). Systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting glycemia, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride (TG), Homeostatic Model Assessment--Insulin Resistance (HOMA-IR), leukocyte count and ultrasensitive C-reactive protein (CRP) were also analyzed. RESULTS There were significant correlations between WHtR and BMI z score (r=0.88, p<0.0001), SBP (r=0.51, p<0.0001), DBP (r=0.49, p<0.0001), LDL (r=0.25, p<0.0008, HDL (r=-0.28, p<0.0002), TG (r=0.26, p<0.0006), HOMA-IR (r=0.83, p<0.0001) and CRP (r=0.51, p<0.0001). WHtR and BMI areas under the curve were similar for all the cardio-metabolic parameters. A WHtR cut-off value of >0.47 was sensitive for screening insulin resistance and any one of the cardio-metabolic parameters. CONCLUSIONS The WHtR was as sensitive as the 2007 WHO BMI in screening for metabolic risk factors in 6-10-year-old children. The public health message "keep your waist to less than half your height" can be effective in reducing cardio-metabolic risk because most of these risk factors are already present at a cut point of WHtR≥0.5. However, as this is the first study to correlate the WHtR with inflammatory markers, we recommend further exploration of the use of WHtR in this age group and other population-based samples.