Study: Obesity epidemic partly explained by erroneous data

A new study in the American Journal of Epidemiology indicates that parent-reported height/weight data for children isn’t all that reliable. We have always been critical of self-reported obesity data.
The abstract is below.
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Parent-Reported Height and Weight as Sources of Bias in Survey Estimates of Childhood Obesity
Margaret M. Weden*, Peter B. Brownell, Michael S. Rendall, Christopher Lau, Meenakshi Fernandes and Zafar Nazarov
↵*Correspondence to Dr. Margaret M. Weden, Rand Corporation, 1776 Main Street, Santa Monica, CA 90401-3208 (e-mail: mweden@rand.org).
Abbreviations: BMI, body mass index; CDC, Centers for Disease Control and Prevention; CI, confidence interval; NLSY79, National Longitudinal Survey of Youth 1979 Cohort; NLSY79-Child, Children of the National Longitudinal Survey of Youth 1979 Cohort; PSID-CDS, Child Development Supplement of the Panel Study of Income Dynamics.
Received June 26, 2012.
Accepted December 3, 2012.
Abstract
Parental reporting of height and weight was evaluated for US children aged 2–13 years. The prevalence of obesity (defined as a body mass index value (calculated as weight (kg)/height (m)2) in the 95th percentile or higher) and its height and weight components were compared in child supplements of 2 nationally representative surveys: the 1996–2008 Children of the National Longitudinal Survey of Youth 1979 Cohort (NLSY79-Child) and the 1997 Child Development Supplement of the Panel Study of Income Dynamics (PSID-CDS). Sociodemographic differences in parent reporting error were analyzed. Error was largest for children aged 2–5 years. Underreporting of height, not overreporting of weight, generated a strong upward bias in obesity prevalence at those ages. Frequencies of parent-reported heights below the Centers for Disease Control and Prevention’s (Atlanta, Georgia) first percentile were implausibly high at 16.5% (95% confidence interval (CI): 14.3, 19.0) in the NLSY79-Child and 20.6% (95% CI: 16.0, 26.3) in the PSID-CDS. They were highest among low-income children at 33.2% (95% CI: 22.4, 46.1) in the PSID-CDS and 26.2% (95% CI: 20.2, 33.2) in the NLSY79-Child. Bias in the reporting of obesity decreased with children’s age and reversed direction at ages 12–13 years. Underreporting of weight increased with age, and underreporting of height decreased with age. We recommend caution to researchers who use parent-reported heights, especially for very young children, and offer practical solutions for survey data collection and research on child obesity.

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