Abstract
Background. Socioeconomic inequalities in obesity are consistently observed in high-income countries. The development of such inequalities across childhood; however, has not been studied using longitudinal data. Methods. Using data from the Avon Longitudinal Study of Parents and Children (participants were born 1991/2 in South-West England), we modelled trajectories of ponderal index (PI) (N=12 246) from birth to 2 years and body mass index (BMI) (N=11 380) from 2 to 10 years. Individual trajectories were estimated using mixed-effects models, and differences in trajectories by socioeconomic position (measured by maternal education) were investigated. Results. There was little socioeconomic patterning of PI from birth to 2 years. Socioeconomic differences in BMI began to emerge by 4 years old, and widened with increasing age. Amongst girls there was a clear gradient across all categories of maternal education by age 8, with daughters of more educated women being less adipose. Amongst boys, sons of degree-educated women had lower BMI but there was little difference between the lower maternal education categories. By 10 years old the mean BMI difference between the highest and lowest maternal education category was 0.38 kg/m2 for boys and 0.89 kg/m2 for girls. The results imply that interventions to prevent inequalities in childhood obesity should begin in pre-school years.
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Acknowledgements
We are extremely grateful to all the families who took part in this study, the midwives for their help in recruiting them, and the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists, and nurses.
We thank Paul Clarke (Centre for Market and Public Organisation, University of Bristol), Fiona Steele (Centre for Multilevel Modelling, University of Bristol), for statistical advice and comments on an earlier draft.
Funding
This work was supported by a grant from the UK Economic and Social Research Council (RES-060-23-0011). This grant provides the salary for LH. BG is funded by a UK Medical Research Council Fellowship in Health of the Public. The UK Medical Research Council; the Wellcome Trust and the University of Bristol provide core funding support for ALSPAC. The UK Medical Research Council and the University of Bristol provide core funding for the MRC Centre of Causal Analyses in Translational Epidemiology. The views expressed in this paper are those of the authors and not necessarily those of any funding body or others whose support is acknowledged. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Declaration of interest: All funding sources are declared in the acknowledgements section. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.