title: Trends in Socioeconomic Inequalities in Body Mass Index, Underweight and Obesity among English Children, 2007-2008 to 2011-2012.
abstract: BACKGROUND
  Socioeconomic inequalities in childhood obesity have been reported in most developed countries, with obesity more common in deprived groups. Whether inequalities are found in the prevalence of underweight, the rest of the body mass index (BMI) distribution, or have changed across time is not clear.
  
  
  RESULTS
  The sample comprised 5,027,128 children on entry (4 to 5 years old) and leaving (10 to 11 years) state primary (elementary) school who participated in the National Child Measurement Programme (England, United Kingdom). We used area-level deprivation (Indices of Multiple Deprivation at the lower super output area) as a measure of socioeconomic deprivation. From 2007-2008 to 2011-2012 inequalities in obesity between the most compared to least deprived group increased (from 7.21% to 8.30%; p<0.001), whereas inequalities in the prevalence of underweight (1.50% to 1.21%; p = 0.15) were stable during this period. There were no differences by age group or by sex, but a three-way interaction suggested inequalities in obesity had increased at a faster rate for 10 to 11 year old girls, than 4 to 5 year old boys, (2.03% vs 0.07%; p<0.001 for interaction). Investigating inequalities across the distribution of zBMI showed increases in mean zBMI (0.18 to 0.23, p<0.001) could be attributed to increases in inequalities between the 50th and 75th centiles of BMI. Using the 2011 to 2012 population attributable risk estimates, if inequalities were halved, 14.04% (95% CI 14.00% to 14.07%) of childhood obesity could be avoided.
  
  
  CONCLUSIONS
  Socioeconomic inequalities in childhood obesity and zBMI increased in England between 2007-2008 and 2011-2012. Inequalities in the prevalence of underweight did not change. Traditional methods of examining inequalities only at the clinical thresholds of overweight and obesity may have led the magnitude of inequalities in childhood BMI to be underestimated.
authors.affiliation: South East Wales Trials Unit (SEWTU), Cardiff University, Cardiff, United Kingdom.|Centre for the Development and Evaluation of Complex Interventions for Public Health Improvement (DECIPHer), Cardiff University, Cardiff, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: White
authors.affiliation: School of Medicine, Stanford University, Stanford, California, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Rehkopf
authors.affiliation: Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Laust Hvas
authors.initials: LH
authors.lastname: Mortensen
mesh_terms: D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000453:epidemiology*; D015995:Prevalence; D012959:Socioeconomic Factors; D013851:Thinness
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