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Socio-economic disparities of childhood body mass index in a newly developed population: evidence from Hong Kong's ‘Children of 1997’ birth cohort
  1. C Mary Schooling,
  2. Cynthia Yau,
  3. Benjamin J Cowling,
  4. Tai Hing Lam,
  5. Gabriel M Leung
  1. Department of Community Medicine and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, PR China
  1. Correspondence to Miss Cynthia Yau, Department of Community Medicine and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Unit 624-627, Level 6, Core F, Cyberport 3, 100 Cyberport Road, Hong Kong, PR China; cynthyau{at}hkucc.hku.hk

Abstract

Background Childhood adiposity in developed countries is often associated with lower socio-economic position (SEP) of the family and neighbourhood. However, the association of adiposity with SEP varies with national income. The authors examined whether childhood BMI was associated with family or neighbourhood socio-economic characteristics in a recently and rapidly developed Chinese population.

Methods The authors used multilevel modelling in Hong Kong's population-representative ‘Children of 1997’ birth cohort (n=8327) to examine the association of BMI z-score and overweight (including obesity) at ages 6–11 years with parental education, mother's birthplace, sex and neighbourhood median income.

Results In 7108 (85 % successful follow-up) children, boys were more adipose than girls. The association of parental education with BMI z-score varied with mother's birthplace (p value for interaction 0.001). In children of Hong Kong-born mothers, parental education was negatively associated with BMI z-score (mean difference –0.15, 95% CI –0.25 to –0.05 for highest compared with lowest). However, in children of mainland China-born mothers, parental education was positively associated with BMI z-score (0.18, 95% CI 0.02 to 0.34 in the same comparison). Neighbourhood had no association with BMI z-score.

Conclusions In this recently developed Chinese population, there was no consistent association between socio-economic characteristics and childhood BMI. Other factors, such as experience of economic transition, as proxied by mother's place of birth, exerted a modifying impact. The cultural and biological mechanisms underlying these socio-historical intergenerational influences need to be determined, so that effective interventions can be implemented in China and elsewhere.

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Footnotes

  • Funding The initial study was supported by the Hong Kong Healthcare & Promotion Fund Committee in Hong Kong (Grant no 216106). Retrieval of additional data in 2005–2006 was funded by the Health and Health Services Research Fund in Hong Kong (Grant no 03040711). Retrieval of geo-spatial identifiers was funded by the Research Fund for the Control of Infectious Diseases in Hong Kong (Grant no 04050172). Recent re-establishment of contact with cohort members was funded by the University Research Committee SRT of Public Health Granted Research, The University of Hong Kong.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the University of Hong Kong-Hospital Authority Hong Kong West Cluster Joint Institutional Review Board and the Ethics Committee of the Department of Health, Government of the Hong Kong SAR.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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