title: Development of socioeconomic inequalities in obesity among Dutch pre-school and school-aged children.
abstract: OBJECTIVE
  To investigate the emergence of the inverse socioeconomic gradient in body mass index (BMI) in the first 6 years of life. Furthermore, associations of socioeconomic position (SEP) with BMI and total fat mass (%) were assessed at age 6, and potential mediating factors in the pathway between SEP and children's body composition were investigated.
  
  
  METHODS
  Nearly 3,656 Dutch children participating in a prospective cohort study in Rotterdam, the Netherlands, were included from 2002 to 2006. Maternal educational level and net household income were used as indicators of SEP. BMI and fat mass were both outcome measures. Associations and mediation analyses were investigated using linear mixed models and linear regression analyses.
  
  
  RESULTS
  The lowest SEP groups showed a larger increase in BMI over time as compared to the highest SEP groups (P < 0.001), which resulted in the emergence of the inverse SEP gradient around 3-4.5 years of age. In 6-year-old children, both BMI and total fat mass were significantly higher for children of low educated mothers (difference in BMI SDS: 0.24; 95% CI 0.15, 0.33; and in total fat mass (%): 2.68; 95% CI 2.19, 3.17), which was also shown for children with a low household income. This was mainly explained by parental BMI and prenatal smoking.
  
  
  CONCLUSIONS
  The inverse socioeconomic gradient in obesity emerges during the preschool period, and widens with increasing age. A public health strategy aimed at tackling the development of inequalities in obesity in early childhood needs to start before birth and should include the prevention of prenatal smoking and obesity of parents.
authors.affiliation: The Generation R Study Group, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Public Health, Erasmus Medical Center, the Netherlands.
authors.forename: Selma H
authors.initials: SH
authors.lastname: Bouthoorn
authors.forename: Anne I
authors.initials: AI
authors.lastname: Wijtzes
authors.forename: Vincent W V
authors.initials: VW
authors.lastname: Jaddoe
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.forename: Hein
authors.initials: H
authors.lastname: Raat
authors.forename: Frank J
authors.initials: FJ
authors.lastname: van Lenthe
mesh_terms: D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004522:Educational Status; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D009765:Obesity / Q000453:epidemiology*; D011247:Pregnancy; D011446:Prospective Studies; D012307:Risk Factors; D012574:Schools / Q000706:statistics & numerical data*; D012959:Socioeconomic Factors