Throwing out the baby with the bathwater?: Comparing 2 approaches to implausible values of change in body size

摘要

BACKGROUND: In childhood obesity research, the appearance of height loss, or "shrinkage," indicates measurement error. It is unclear whether a common response - excluding "shrinkers" from analysis - reduces bias. METHODS: Using data from the National Longitudinal Study of Adolescent Health, we sampled 816 female adolescents (≥17 years) who had attained adult height by 1996 and for whom adult height was consistently measured in 2001 and 2008 ("gold-standard" height). We estimated adolescent obesity prevalence and the association of maternal education with adolescent obesity under 3 conditions: excluding shrinkers (for whom gold-standard height was less than recorded height in 1996), retaining shrinkers, and retaining shrinkers but substituting their gold-standard height. RESULTS: When we estimated obesity prevalence, excluding shrinkers decreased precision without improving validity. When we regressed obesity on maternal education, excluding shrinkers produced less valid and less precise estimates. CONCLUSION: In some circumstances, ignoring shrinkage is a better strategy than excluding shrinkers.