The preventive effect of breast-feeding for longer than 6 months on early pubertal development among children aged 7-9 years in Korea

Objective: The present study was performed to investigate whether breast-feeding is associated with early pubertal development among children 7-9 years old in Korea. Design: Children were divided into those who did and did not receive breast-feeding for 6 months or longer in accordance with the recommendations of the WHO. Pubertal status was determined by clinical examination using Tanner staging. Setting: Prospective observational study. Subjects: We conducted a follow-up study of children aged 7-9 years in 2011 who had taken part in the Ewha Birth & Growth Cohort study. Results: Fifty (22.8 %) of the total of 219 children were in early puberty, with the proportion being slightly higher for girls (24.1 %) than boys (21.4 %). Children who had entered early puberty were taller, weighed more and had a higher concentration of insulin-like growth factor 1. Moreover, the change in weight Z-score from birth to follow-up was significantly lower in children who were breast-fed than in those who were not (weight Z-score change: 0.32 (sd 1.59) v. 0.77 (sd 1.61), respectively, P=0.04). Comparison of breast-feeding by puberty status indicated a preventive association with early puberty in children who were breast-fed for 6 months or longer (OR=0.37; 95 % CI 0.18, 0.74). This association remained significant after adjustment for relevant covariates. Conclusions: These results demonstrate a beneficial association between breast-feeding and early pubertal development, especially in those breast-fed for 6 months or longer. The study suggests that interventions would need to start early in life to prevent early pubertal development.