Infant Growth and Onset of Puberty: Prospective Observations from Hong Kong's "Children of 1997" Birth Cohort

PURPOSE: Infant growth and early puberty are associated with the risk of cardiovascular disease. It is unclear whether pubertal timing has an independent etiologic role or is a marker of preceding growth. We examined whether infant growth was associated with age at pubertal onset and whether any associations were mediated by childhood height or body mass index. METHODS: We used multivariable interval censored proportional hazards regression in 6873 term births (87% follow-up, 53% male) from a population representative Hong Kong Chinese birth cohort, "Children of 1997." We examined the adjusted associations of sex specific infant growth trajectories, derived from latent class analyses by the use of, on average, 4.2 measurements per child, with clinically assessed age at pubertal onset (Tanner stage II). We used Sobel tests to assess mediation. RESULTS: Compared with children of average birth weight whose weight followed the same centile curve, a faster weight growth trajectory from birth to 12 months was associated with earlier pubertal onset (time ratio, 0.979; 95% confidence interval, 0.965-0.993) among boys, whereas girls born light with slow infant growth had later puberty (time ratio 1.020, 95% confidence interval 1.006-1.034). These associations were mediated by both height and body mass index among girls but only by height in boys. CONCLUSIONS: Infant weight growth may be associated with earlier pubertal onset, particularly in boys, at least in part because it is associated with more linear growth in childhood. Earlier pubertal onset may be an indicator of up-regulation of growth axes related to the risk of cardiovascular disease. Ann Epidemiol 2012;22:43-50. (C) 2012 Elsevier Inc. All rights reserved.