title: Is informal child care associated with childhood obesity? Evidence from Hong Kong's "Children of 1997" birth cohort.
abstract: BACKGROUND
  In Western populations, informal child care is associated with childhood obesity. However, informal child care and obesity share social patterning making evidence from other settings valuable.
  
  
  METHODS
  We used multivariable linear and logistic regression models to estimate the association of child care at 6 months and at 3, 5 and 11 years with body mass index (BMI) z-score and overweight (including obesity) at 11 years in a Hong Kong Chinese birth cohort. We assessed whether associations varied with sex or socio-economic position (SEP). We used multiple imputation for missing exposures and confounders.
  
  
  RESULTS
  Of the original 8327 cohort members, 7933 are alive, participating and living in Hong Kong. At ~11 years, 6796 had their BMI clinically assessed. Higher SEP was associated with informal care. After imputation, informal care at each of 3, 5 or 11 years was separately associated with higher BMI z-score [3 years 0.10, 95% confidence interval (CI) 0.03-0.18, 5 years 0.12, 95% CI 0.04-0.21, 11 years 0.17, 95% CI 0.04-0.31] and with the presence of overweight [odds ratio (OR) 3 years 1.19, 95% CI 1.03-1.37, 5 years OR 1.20, 95% CI 1.03-1.40, 11 years OR 1.21, 95% CI 1.02-1.45], adjusted for sex, SEP and birth weight z-score. Current informal care had the strongest association. However, informal child care at 5 years also contributed. There was no evidence of differences by sex or SEP.
  
  
  CONCLUSIONS
  In a developed, non-Western setting, informal child care was associated with childhood obesity. Modifiable attributes of informal child care warrant investigation for obesity prevention.
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 SAR, People's Republic of China.
authors.forename: Shi Lin
authors.initials: SL
authors.lastname: Lin
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Leung
authors.forename: Lai Ling
authors.initials: LL
authors.lastname: Hui
authors.forename: Tai Hing
authors.initials: TH
authors.lastname: Lam
authors.forename: C Mary
authors.initials: CM
authors.lastname: Schooling
mesh_terms: D015992:Body Mass Index; D002648:Child; D002654:Child Care / Q000379:methods / Q000706:statistics & numerical data*; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007223:Infant; D008297:Male; D009765:Obesity / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology*; D012044:Regression Analysis; D012307:Risk Factors; D017678:Sex Distribution; D012959:Socioeconomic Factors