Abstract
Objectives
Income inequality has been linked to high and unhealthy body mass index (BMI), though there is a dearth of evidence in adolescents. Therefore, this study examines the association between income inequality and BMI in a large sample of Canadian adolescents.
Methods
A pooled cross-sectional design was used. Participants were adolescents (n = 101,901) from 157 Canadian secondary schools participating in the 2016–2017, 2017–2018, or 2018–2019 waves of the Cannabis, Obesity, Mental health, Physical activity, Alcohol, Smoking, and Sedentary behaviour (COMPASS) study. BMI was calculated from self-reported height and weight and converted to World Health Organization (WHO) z-BMI scores. Gini coefficients were calculated at the census division level (n = 49) using data from the 2016 Canadian Census. Multilevel modelling was performed to account for the clustering of students nested within schools, which were nested within census divisions. Interactions were included to determine whether associations were heterogeneous for males and females.
Results
Income inequality demonstrated a non-linear association with WHO z-BMI score (z-Gini: β = 0.05, 95%CI: 0.02, 0.08; z-Gini2: β = −0.02, 95% CI: −0.04, −0.01) among adolescents after adjusting for student-, school-, and census division–level covariates. This association was more pronounced among females.
Conclusion
The association between income inequality and BMI, being overweight, or having obesity appears to be non-linear. Public health units and schools may benefit from incorporating upstream factors such as income inequality into their interventions attempting to promote healthy weights.
Résumé
Objectifs
L’inégalité des revenus a été liée à un indice de masse corporelle (IMC) élevé et malsain, bien qu’il y ait un manque de preuves chez les adolescents. Par conséquent, la présente étude examine l’association entre l’inégalité des revenus et l’IMC dans un vaste échantillon d’adolescents canadiens.
Méthodes
Un devis comprenant des études transversales groupées a été utilisé. Les participants étaient des adolescents (n = 101 901) de 157 écoles secondaires canadiennes participant aux vagues 2016-2017, 2017-2018 ou 2018-2019 de l’étude COMPASS (Cannabis, Obésité, Santé mentale, Activité physique, Alcool, Tabagisme et Comportement sédentaire). L’IMC a été calculé à partir de la taille et du poids auto-déclarés et convertis en scores z selon l’Organisation mondiale de la santé (OMS). Les coefficients de Gini ont été calculés à l’échelle du secteur de recensement (n = 49) en utilisant les données du Recensement canadien de 2016. Des modèles multiniveaux ont été effectués pour tenir compte du regroupement des élèves dans les écoles, qui elles-mêmes étaient incluses dans les secteurs de recensement. Des variables d’interactions ont été incluses dans les modèles afin de permettre une comparaison des paramètres estimés entre les hommes et les femmes.
Résultats
L’inégalité des revenus a démontré une association non linéaire avec le score de l’IMC z de l’OMS (z-Gini : β = 0,05, IC à 95 % : 0,02, 0,08; z-Gini2 : β = -0,02, IC à 95 % : -0,04, -0,01) chez les adolescents après ajustement pour tenir compte des covariables au niveau des élèves, de l’école et des divisions de recensement. Cette association était plus prononcée chez les femmes.
Conclusion
L’association entre l’inégalité des revenus et l’IMC, l’embonpoint ou l’obésité semble être non linéaire. Les bureaux de santé publique et les écoles pourraient tirer profit de l’intégration de facteurs en amont comme l’inégalité des revenus dans leurs interventions visant à promouvoir le poids santé.
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Data availability
Access can be made available by request through the COMPASS project website: https://uwaterloo.ca/compass-system/compass-system-projects/compass-study.
Code availability
Stata code for statistical analysis is available upon request to the corresponding author.
Change history
19 October 2023
A Correction to this paper has been published: https://doi.org/10.17269/s41997-023-00819-9
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Funding
The COMPASS study has been supported by a bridge grant from the CIHR Institute of Nutrition, Metabolism and Diabetes (INMD) through the “Obesity – Interventions to Prevent or Treat” priority funding awards (OOP-110788), an operating grant from the CIHR Institute of Population and Public Health (IPPH) (MOP-114875), CIHR project grants (PJT-148562 and PJT-159693), a CIHR bridge grant (PJT-149092), a research funding arrangement with Health Canada (#1617-HQ-000012), and the Women & Children’s Health Research Institute Innovation Grant (#3161). Pabayo is a Canada Research Chair Tier II in social and health inequities.
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Pabayo and Leatherdale were responsible for the study conception and design. Material preparation and data collection were performed by Leatherdale and Pabayo. Statistical analyses were performed by Hunter and Veerasingam. The first draft of the manuscript was written by Hunter and all authors commented on previous versions of the manuscript and approved the final manuscript for submission.
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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (University of Alberta: Ethics # Pro00040729; and University of Waterloo: Ethics # ORE 30118) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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This article was updated. The β value in the abstracts was corrected from “β = 0.50” to “β = 0.050”.
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Hunter, S., Veerasingam, E., Barnett, T.A. et al. The association between income inequality and adolescent body mass index: findings from the COMPASS study (2016–2019). Can J Public Health 114, 1006–1015 (2023). https://doi.org/10.17269/s41997-023-00798-x
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DOI: https://doi.org/10.17269/s41997-023-00798-x