title: Timing of solid food introduction and obesity: Hong Kong's "children of 1997" birth cohort.
abstract: BACKGROUND
  Some observational studies in Western settings show that early introduction of solid food is associated with subsequent obesity. However, introduction of solid food and obesity share social patterning. We examined the association of the timing of the introduction of solid food with BMI and overweight (including obesity) into adolescence in a developed non-Western setting, in which childhood obesity is less clearly socially patterned.
  
  
  METHODS
  We used generalized estimating equation models to estimate the adjusted associations of the timing of the introduction of solid food (<3, 3-4, 5-6, 7-8, and >8 months) with BMI z score and overweight (including obesity) at different growth phases (infancy, childhood, and puberty) in 7809 children (88% follow-up) from a Chinese birth cohort, "Children of 1997." We assessed if the associations varied with gender or breastfeeding. We used multiple imputation for missing exposure and confounders.
  
  
  RESULTS
  The introduction of solid food at <3 months of age was associated with lower family socioeconomic position (SEP) but was not clearly associated with BMI or overweight (including obesity) in infancy [mean difference in BMI z score: 0.01; 95% confidence interval (CI): -0.14 to 0.17], childhood (0.14; 95% CI: -0.11 to 0.40), or at puberty (0.22; 95% CI: -0.07 to 0.52), adjusted for SEP and infant and maternal characteristics.
  
  
  CONCLUSIONS
  In a non-Western developed setting, there was no clear association of the early introduction of solid food with childhood obesity. Together with the inconsistent evidence from studies in Western settings, this finding suggests that any observed associations might simply be residual confounding by SEP.
authors.affiliation: Lifestyle and Life Course Epidemiology Group, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, PR China.
authors.forename: Shi Lin
authors.initials: SL
authors.lastname: Lin
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Leung
authors.forename: Tai Hing
authors.initials: TH
authors.lastname: Lam
authors.forename: C Mary
authors.initials: CM
authors.lastname: Schooling
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D001942:Breast Feeding / Q000706:statistics & numerical data; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007225:Infant Food; D008297:Male; D015233:Models, Statistical; D009765:Obesity / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D018570:Risk Assessment; D012959:Socioeconomic Factors; D013997:Time Factors
keywords: China; cohort study; infant feeding; obesity; solid food