Objective: To evaluate whether there is an association between the body mass index z-score and waist-to-height ratio of children and adolescents.
Methods: This was a cross-sectional study conducted in a school in Santo André, SP, between June and August 2019. Body mass index was measured for all participants, adopting the z-score cutoff of +2 recommended by the World Health Organization. The waist-to-height ratio was determined in children over two years of age and considered abnormal when ≥0.5. The qualitative variables are presented as absolute numbers and percentages. To compare qualitative data, we used the χ2 test or Fisher's exact test. Pearson's test was applied to assess the correlation between BMI and waist-to-height ratio. The level of significance adopted was 5%.
Results: The body mass index was calculated for 518 children and the waist-to-height ratio for 473 children. Regarding body mass index, 60.6% of the participants had normal weight, 3.1% were underweight, and 36.3% were overweight. overweight (24.7%) and obesity (22.7%) were more prevalent in adolescents. The waist-to-height ratio was abnormal in 50.5% of the sample. There was an increasing association between body mass index and waist-to-height ratio with age, according to the Pearson correlation coefficients for the age groups <5 years (r=0.459; p<0.001), 5 to 10 years (r=0.687; p<0.001) and >10 years (r=0.805; p<0.001).
Conclusion: There was a significant correlation between body mass index and waist-to-height ratio. This association was higher in adolescents. The waist-to-height ratio is easy to apply and may be useful as a predictor of cardiometabolic risk.