Grandparental education, parental education and child height: Evidence from Hong Kong's "Children of 1997" birth cohort

Purpose: Adult height is the sum of growth during fetal, infancy, childhood, and puberty, controlled by different biological factors. In long-term developed Western populations, height is positively associated with socioeconomic position, but less clearly so in recently developing populations. We aimed to elucidate socioeconomic influences on height at different growth phases. Methods: We examined the associations of parents' education and grandparents' education with birth weight and height gain z-scores during infancy (birth to <2years), childhood (2 to <8years), and puberty (8 to <14years) adjusted for parents' height using generalized estimating equations in Hong Kong's "Children of 1997" birth cohort (n= 8264). Results: Parents' education, but not grandparents', was positively associated with birth weight (z-score, 0.07; 95% confidence interval [CI] 0.01-0.12 for grade ≥12compared with grade ≤9) and height gain during infancy (0.11; 95% CI, 0.05-0.18), adjusted for gender, gestational age, initial size, parity, parents' age, parents' birthplace, and parents' height. Conversely, similarly adjusted, grandparents' education, but not parents', was associated with height gain during childhood (0.11; 95% CI, 0.04-0.18). Conclusions: Parental education was associated with fetal and infant, but not childhood, linear growth, suggesting the mechanism underlying socioeconomic influences on height at different growth phases may be contextually specific.