Socioeconomic differences in childhood growth trajectories: at what age do height inequalities emerge?
- Laura D Howe1,2,
- Kate Tilling1,
- Bruna Galobardes1,
- George Davey Smith1,2,
- David Gunnell1,
- Debbie A Lawlor1,2
- 1Department of Social Medicine, University of Bristol, Bristol, UK
- 2MRC Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, UK
- Correspondence to Dr Laura D Howe, MRC Centre for Causal Analyses in Translational Epidemiology, Oakfield House, Oakfield Grove, Bristol BS8 2BN, UK;
Contributors LDH, DAL and KT conceptualised the study and designed the study methodology. LDH carried out data analysis and wrote the first draft of the manuscript. All authors contributed to data interpretation and to critical revisions of the manuscript.
- Accepted 31 May 2010
- Published Online First 18 August 2010
Background Socioeconomic differentials in adult height are frequently observed, but the age at which these inequalities emerge and the patterns they follow through childhood are unknown.
Subjects and Methods Using data from the Avon Longitudinal Study of Parents and Children (ALSPAC), height trajectories from birth to 10 years (N=12366) were modelled. Individual trajectories were estimated using mixed-effects models. Differences in trajectories by socioeconomic position (SEP) were investigated.
Results There was a clear gradient in birth length across categories of maternal education; average birth length in boys was 0.41 cm lower in the lowest maternal education category compared with the highest, which is 0.9% of the average birth length for the highest SEP category (equivalent results for girls 0.65 cm, 1.3%). Socioeconomic differences in childhood growth were small, and only resulted in minimal widening of the height inequality with increasing age. By the age of 10 years, the mean difference between children in the lowest and highest maternal education categories was 1.4 cm for boys and 1.7 cm for girls; similar proportionate differences to those seen at birth (1.0% for boys and 1.2% for girls). Patterns were the same when father's education or household occupational social class were used to measure SEP.
Conclusions The socioeconomic differential in height during childhood in this cohort of children born in the UK in the 1990s arises largely through inequalities in birth length, with small increases in the inequality from differences in growth in later childhood.
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 LDH. BG is funded by a UK Medical Research Council fellowship in health of the public. DG is a National Institute of Health research senior investigator. The UK Medical Research Council; the Wellcome Trust and the University of Bristol provide core funding support for the Avon Longitudinal Study of Parents and Children. 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.
Competing interests None.
Ethics approval Ethics approval for the study was obtained from the ALSPAC Law and Ethics Committee and the Local Research Ethics Committees.
Provenance and peer review Not commissioned; externally peer reviewed.
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