The association between family structure and children’s BMI over time - the mediating role of income

Burkill, Sarah; Waterhouse, Philippa and Pazzagli, Laura (2021). The association between family structure and children’s BMI over time - the mediating role of income. Annals of Epidemiology, 55 pp. 83–90.



Purpose: Whilst both family structure and income have previously been indicated as being associated with body mass index (BMI), the extent to which the effect of family structure on BMI is mediated through income is incompletely understood. Taking the case of the United Kingdom, this study aims to investigate the association between family structure, defined in this study as whether children live in a one or two adult household, and childhood BMI, and whether this varies by child sex and with increased age. Secondly, the study aims to examine whether family equivalised income as a proxy for socio-economic status, mediates the association between family structure and child’s BMI.

Methods: This study uses data from the Millennium Cohort Study (MCS). Data from 7,478 children born between 2000 and 2001 in the UK at the ages of 3, 5, 7, 11, and 14 was used. Mediation analysis was used to consider, at each age, the extent to which the association between living in a one or two adult household and BMI was mediated through income overall, and stratified by sex. To assess the robustness of the mediation analysis estimates, we used both E-values, and multiple confounder adjustment.

Results: At ages 3 and 5, there was no direct or indirect effect of family structure mediated by income on BMI. From the age of 7 to 11, the overall proportion of the association mediated vastly increased, from 19.70% at age 7 up to 42.70% at the age of 11. The E-values show that substantial unmeasured confounder associations would be needed to fully explain away the conclusions from the mediation analysis. Results remained significant when models were additionally adjusted for geographic region, main respondent’s (usually mother’s) highest educational attainment, and ethnicity.

Conclusions: An increasing proportion of the association between family structure and BMI is mediated by income as children grow older. The study focuses on the mediating role of income between family structure and BMI using the available data as an empirical application of the potential impact of income as mediator in the causal pathway.

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  • Item ORO ID
  • 73288
  • Item Type
  • Journal Item
  • ISSN
  • 1047-2797
  • Keywords
  • family structure; children's BMI; socioeconomic status; mediation
  • Academic Unit or School
  • Faculty of Wellbeing, Education and Language Studies (WELS)
  • Copyright Holders
  • © 2020 Elsevier
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  • Jisc Publications-Router
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  • ORO Import