Socioeconomic differences in childhood length/height trajectories in a middle-income country: a cohort study

Abstract

BackgroundSocioeconomic disadvantage is associated with shorter adult stature. Few studies have examined socioeconomic differences in stature from birth to childhood and the mechanisms involved, particularly in middle-income former Soviet settings.MethodsThe sample included 12,463 Belarusian children (73% of the original cohort) born in 1996–1997, with up to 14 stature measurements from birth to 7 years. Linear spline multi-level models with 3 knots at 3, 12 and 34 months were used to analyse birth length and growth velocity during four age-periods by parental educational achievement (up to secondary school, advanced secondary/partial university, completed university) and occupation (manual, non-manual).ResultsGirls born to the most (versus least) educated mothers were 0.43 cm (95% confidence interval (CI): 0.28, 0.58) longer at birth; for boys, the corresponding difference was 0.30 cm (95% CI: 0.15, 0.46). Similarly, children of the most educated mothers grew faster from birth-3 months and 12–34 months (p-values for trend ≤0.08), such that, by age 7 years, girls with the most (versus least) educated mothers were 1.92 cm (95% CI: 1.47, 2.36) taller; after controlling for urban/rural and East/West area of residence, this difference remained at 1.86 cm (95% CI: 1.42, 2.31), but after additionally controlling for mid-parental height, attenuated to 1.10 cm (95% CI: 0.69, 1.52). Among boys, these differences were 1.95 cm (95% CI: 1.53, 2.37), 1.89 cm (95% CI: 1.47, 2.31) and 1.16 cm (95% CI: 0.77, 1.55), respectively. Additionally controlling for breastfeeding, maternal smoking and older siblings did not substantively alter these findings. There was no evidence that the association of maternal educational attainment with growth differed in girls compared to boys (p for interaction = 0.45). Results were similar for those born to the most (versus least) educated fathers, or who had a parent with a non-manual (versus manual) occupation.ConclusionsIn Belarus, a middle-income former Soviet country, socioeconomic differences in offspring growth commence in the pre-natal period and generate up to approximately 2 cm difference in height at age 7 years. These associations are partly explained by genetic or other factors influencing parental stature.Trial RegistrationCurrent Controlled Trials: NCT01352247 assigned 9 Sept 2005; ClinicalTrials.gov. Identifier: NCT01561612 received 20 Mar 2012.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2458-14-932) contains supplementary material, which is available to authorized users.

Socioeconomic differences in children’s growth trajectories from infancy to early adulthood: evidence from four European countries

“…Consistent with this position, Galobardes et al 31 found that midparental height (average of mother and father’s height) fully explained the initial difference in children’s height. Others by contrast have found that parental height is not a sufficient explanation for socioeconomic differences in height,18 although the latter study is from a low-income to middle-income country. In any event, one could argue that this explanation is not particularly convincing because it simply shifts the debate back a generation and makes one query whether it was more advantageous environmental exposures in the parent’s generation that led to the development of taller parents (ie, intergenerational reproduction of inequalities).…”

“…Although, studies have shown that social inequalities in children’s length/height are already apparent at time of birth, it remains unclear whether the differences remain stable,9 narrow11 or widen18 as children age. Furthermore, many of the recent studies are based on relatively old data from British cohorts 9–11 19.…”

Effects of Promoting Long-term, Exclusive Breastfeeding on Adolescent Adiposity, Blood Pressure, and Growth Trajectories

“…We parameterized the relationships of weight, stature or BMI z-score with age using linear splines with 5 knot points at 3 months, 12 months, 2.8 years, 8.5 years and 14.5 years to describe periods of approximately linear growth based on the data. (38) Although a linear spline model is an approximation of the true non-linear growth function, its coefficients are easily interpretable and have produced a good model fit in this and other cohorts. (39–44) The knot points at 8.5 and 14.5 years were chosen because those were the oldest ages at the 6.5- and 11.5-year follow-ups.…”

A Review of the Relationship Between Socioeconomic Position and the Early-Life Predictors of Obesity

“…Studies from the Netherlands, Australia and the UK found no association between infant growth and SEP [104,105,108] (with the Australian study assessing rapid infant weight gain), with four European studies from the UK, Netherlands and Sweden finding an inverse association [106,107,109,110] (Wiljaars finding an association with rapid weight gain and Svensson finding an association with overall weight gain but not rapid weight gain). Only two studies were conducted in low-or middle-income countries, with a positive association observed in infants from both Belarus [111] and Chile (noting that the Chilean sample excluded babies <3 kg at birth) [112].…”