Objective: To assess parental understanding of body mass index (BMI) and BMI percentiles by using standard versus color-coded charts; to investigate how parental literacy and/or numeracy (quantitative skills) affects that understanding.
Methods: A convenience sample of 163 parents of children aged 2 to 8 years at 2 academic pediatric centers completed a demographics questionnaire, the mathematics portion of the Wide Range Achievement Test (WRAT-3R), the Short Test of Functional Health Literacy in Adults (S-TOFHLA), and an "Understanding BMI" questionnaire, which included parallel BMI charting questions to compare understanding of standard versus color-coded BMI charting. Outcomes included parental-reported versus actual understanding of BMI, the odds (obtained by generalized estimating equations) of answering parallel questions correctly by using standard versus color-coded charting, and odds of answering questions correctly on the basis of numeracy and literacy.
Results: Many parents (60%) reported knowing what BMI was, but only 30% could define it even roughly correctly. When parents used color-coded charts, they had greater odds of answering parallel BMI charting questions correctly than when they used standard charts (mean, 88% vs 65% correct; pooled adjusted odds ratio, 4.32; 95% confidence interval, 3.14-5.95; P < .01). Additionally, parents with lower numeracy (K-5 level) benefited more from color-coded charts (increased from 51% to 81% correct) than did higher numeracy parents (high school level or greater), who performed well with both charts (89% vs 99% correct).
Conclusions: Parents consistently performed better with color-coded than standard BMI charts. Color-coding was particularly helpful for lower numeracy parents. Future studies should investigate whether these results translate into the office setting and whether understanding motivates parents to implement important lifestyle changes.