Evaluation of Bias in Estimates of Early Childhood Obesity from Parent-Reported Heights and Weights

Published in: American Journal of Public Health, v. 104, no. 7, July 2014, p. 1255-1262

Posted on RAND.org on April 08, 2015

by Michael S. Rendall, Margaret M. Weden, Christopher Lau, Peter Brownell, Zafar Nazarov, Meenakshi Maria Fernandes

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OBJECTIVES: We evaluated bias in estimated obesity prevalence owing to error in parental reporting. We also evaluated bias mitigation through application of Centers for Disease Control and Prevention's biologically implausible value (BIV) cutoffs. METHODS: We simulated obesity prevalence of children aged 2 to 5 years in 2 panel surveys after counterfactually substituting parameters estimated from 1999-2008 National Health and Nutrition Examination Survey data for prevalence of extreme height and weight and for proportions obese in extreme height or weight categories. RESULTS: Heights reported below the first and fifth height-for-age percentiles explained between one half and two thirds, respectively, of total bias in obesity prevalence. Bias was reduced by one tenth when excluding cases with height-for-age and weight-for-age BIVs and by one fifth when excluding cases with body mass-index-for-age BIVs. Applying BIVs, however, resulted in incorrect exclusion of nonnegligible proportions of obese children. CONCLUSIONS: Correcting the reporting of children's heights in the first percentile alone may reduce overestimation of early childhood obesity prevalence in surveys with parental reporting by one half to two thirds. Excluding BIVs has limited effectiveness in mitigating this bias.

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