title: Alternative regression models to assess increase in childhood BMI.
abstract: BACKGROUND
  Body mass index (BMI) data usually have skewed distributions, for which common statistical modeling approaches such as simple linear or logistic regression have limitations.
  
  
  METHODS
  Different regression approaches to predict childhood BMI by goodness-of-fit measures and means of interpretation were compared including generalized linear models (GLMs), quantile regression and Generalized Additive Models for Location, Scale and Shape (GAMLSS). We analyzed data of 4967 children participating in the school entry health examination in Bavaria, Germany, from 2001 to 2002. TV watching, meal frequency, breastfeeding, smoking in pregnancy, maternal obesity, parental social class and weight gain in the first 2 years of life were considered as risk factors for obesity.
  
  
  RESULTS
  GAMLSS showed a much better fit regarding the estimation of risk factors effects on transformed and untransformed BMI data than common GLMs with respect to the generalized Akaike information criterion. In comparison with GAMLSS, quantile regression allowed for additional interpretation of prespecified distribution quantiles, such as quantiles referring to overweight or obesity. The variables TV watching, maternal BMI and weight gain in the first 2 years were directly, and meal frequency was inversely significantly associated with body composition in any model type examined. In contrast, smoking in pregnancy was not directly, and breastfeeding and parental social class were not inversely significantly associated with body composition in GLM models, but in GAMLSS and partly in quantile regression models. Risk factor specific BMI percentile curves could be estimated from GAMLSS and quantile regression models.
  
  
  CONCLUSIONS
  GAMLSS and quantile regression seem to be more appropriate than common GLMs for risk factor modeling of BMI data.
authors.affiliation: Ludwig-Maximilians University of Munich, Division of Pediatric Epidemiology, Institute of Social Pediatrics and Adolescent Medicine, Munich, Germany. andreas.beyerlein@med.uni-muenchen.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Beyerlein
authors.forename: Ludwig
authors.initials: L
authors.lastname: Fahrmeir
authors.forename: Ulrich
authors.initials: U
authors.lastname: Mansmann
authors.forename: André M
authors.initials: AM
authors.lastname: Toschke
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D003627:Data Interpretation, Statistical; D005247:Feeding Behavior; D005260:Female; D005858:Germany; D006801:Humans; D016013:Likelihood Functions; D016014:Linear Models; D009765:Obesity / Q000209:etiology*; D010290:Parents; D011247:Pregnancy; D012044:Regression Analysis; D012307:Risk Factors; D012737:Sex Factors; D012959:Socioeconomic Factors; D013690:Television; D015430:Weight Gain
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