Background Secular trends in the average height of European populations show that adult human height is influenced by environmental as well as genetic factors. Studies have repeatedly shown that height is socially patterned within societies by social position with individuals from more deprived social backgrounds significantly shorter. Currently, evidence is mixed as to whether height differentials by social position increase or decrease with child age or are stable from birth. Because height is strongly correlated with future health and life expectancy, the answer has important implications for life course models of health inequalities.
Methods Data on child height and maternal education from six child cohort studies and four countries (Ireland, UK, Portugal and Finland) are harmonised. Child height within age group, cohort study and country are standardised using z-scores. Height differentials by maternal educational level are estimated using latent growth models of child height trajectory from age 9 months to 21 years using mixed hierarchical models with fixed and random components for each child cohort study.
Results A clear educational gradient in height was evident across all European countries at all age ranges, although the magnitude of the associations varied by country and age group. In Ireland and the UK, there is evidence of growing social inequalities in height from infancy into adolescence from approximately 0.15 to 0.3 of a standard deviation. In Finland, the differential is fairly stable at 0.20 of a z-score score between 3–12 years but narrows between 12 and 24 years of age. The Portuguese data also demonstrate a narrowing of the social gradient from adolescence into adulthood.
Discussion Understanding of the role of early life exposures to later disease processes is still limited. Our results suggest that environmental factors in early childhood interact with a biological substrate to produce increasing child height differentials in early childhood followed by incomplete catch-up in adolescence leading to educational differentials in adulthood. Our results suggest that social environment may shape differentials in both the tempo and absolute level of child height gain with age. The paper provides supportive evidence for the Strachan-Sheikh (2004) model of development with slower growth and lower terminal height among disadvantaged groups a proxy for lower capacity development with implications for life course inequalities in health.
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