Socioeconomic differences in childhood BMI trajectories in Belarus

Richard M Martin,Emily Nicoli,Michael S Kramer,Emily Oken,Kate Tilling,Rachael A Hughes,Debbie A Lawlor,Rita Patel,Laura D Howe,Lidia Matush,Natalia Bogdanovich

doi:10.1038/s41366-018-0042-0

Abstract

ObjectiveTo examine associations of parental socioeconomic position with early-life offspring body mass index (BMI) trajectories in a middle-income country.SubjectsOverall, 12,385 Belarusian children born 1996–97 and enrolled in a randomised breastfeeding promotion trial at birth, with 3–14 measurements of BMI from birth to 7 years.MethodsCohort analysis in which exposures were parental education (common secondary or less; advanced secondary or partial university; completed university) and occupation (manual; non-manual) at birth, and the outcome was BMI z-score trajectories estimated using multilevel linear spline models, controlling for trial arm, location, parental BMI, maternal smoking status and number of older siblings.ResultsInfants born to university-educated mothers were heavier at birth than those born to secondary school-educated mothers [by 0.13 BMI z-score units (95% confidence interval, CI: 0.07, 0.19) for girls and 0.11 (95% CI: 0.05, 0.17) for boys; equivalent for an infant of average birth length to 43 and 38 g, respectively]. Between the ages of 3–7 years children of the most educated mothers had larger BMI increases than children of the least educated mothers. At age 7 years, after controlling for trial arm and location, children of university-educated mothers had higher BMIs than those born to secondary school-educated mothers by 0.11 z-score (95% CI: 0.03, 0.19) among girls and 0.18 (95% CI: 0.1, 0.27) among boys, equivalent to differences in BMI for a child of average height of 0.19 and 0.26 kg/m2, respectively. After further controlling for parental BMI, these differences attenuated to 0.08 z-score (95% CI: 0, 0.16) and 0.16 z-score (95% CI: 0.07, 0.24), respectively, but changed very little after additional adjustment for number of older siblings and mother’s smoking status. Associations were similar when based on paternal educational attainment and highest household occupation.ConclusionsIn Belarus, consistent with some middle-income countries, higher socioeconomic position was associated with greater BMI trajectories from age 3 onwards.

Highlights

Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Overweight and obesity among school-aged and adolescent children have increased among all countries, including those of Eastern Europe [1]
By understanding when differential growth rates arise between socioeconomic groups, we can indicate the important period during childhood when socioeconomic differences first emerge, and contrast these findings with those of other countries
We examine the age at which socioeconomic differences in body mass index (BMI) z-score trajectories emerge, and the extent to which these early-life differences are explained by factors related to childhood adiposity and socioeconomic position: parental size, maternal smoking status and number of older siblings [18,19,20,21]

Summary

Introduction

Overweight and obesity among school-aged and adolescent children have increased among all countries, including those of Eastern Europe [1]. These countries have distinctly differing political, social and economic histories compared to Western developed countries. Systematic reviews of cross-sectional studies show that, in countries with low levels of economic development, obesity is more common among children from more affluent or more educated families [4, 5]. In economically developed (Western) countries, obesity is more common among less affluent or less educated families [4, 6] These cross-sectional analyses cannot indicate the age at which early-life socioeconomic differences in obesity emerge, nor changes in the association with age [5]. By understanding when differential growth rates arise between socioeconomic groups, we can indicate the important period during childhood when socioeconomic differences first emerge, and contrast these findings with those of other countries

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Discussion

Conclusion