title: Throwing out the baby with the bathwater?: Comparing 2 approaches to implausible values of change in body size.
abstract: 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.
  
  
  CONCLUSIONS
  In some circumstances, ignoring shrinkage is a better strategy than excluding shrinkers.
authors.affiliation: From the aDepartment of Epidemiology, University of North Carolina at Chapel Hill, Gillings School of Global Public Health, Chapel Hill, NC; and bUniversity of North Carolina at Chapel Hill, Carolina Population Center, Chapel Hill, NC.W.R.R. and C.L.G. were supported by the 2012 Junior Faculty Development Award, University of North Carolina at Chapel Hill.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Gray
authors.forename: Whitney R
authors.initials: WR
authors.lastname: Robinson
mesh_terms: D000293:Adolescent; D000886:Anthropometry / Q000379:methods; D001827:Body Height; D049628:Body Size; D001835:Body Weight; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D009765:Obesity / Q000453:epidemiology; D015203:Reproducibility of Results; D012107:Research Design; D014481:United States / Q000453:epidemiology; D015431:Weight Loss