Association between complementary food introduction before age 4 months and body mass index at age 5-7 years: A retrospective population-based longitudinal cohort study.

BACKGROUND: The optimal time of starting complementary foods (CFs) in infants remains a subject of debate. This population-based longitudinal cohort study evaluated the association between early CF introduction and body mass index (BMI) in children aged 5-7 years. METHODS: The present study included 917,707 children born in Korea during 2008-2009. Initial timing of CF introduction was obtained by questionnaires administered between 4 and 6 months and 9 and 12 months of age. The cohort consisted of 154,565 eligible individuals who properly completed the screening programme, including structured questionnaires, anthropometric measurements and physical examinations. To balance baseline characteristics, children were subjected to propensity score matching based on 95 covariates, including indicators of baseline health such as perinatal condition, birth weight, economic status, clinical disease and drug exposure. Exposure was defined as introduction to CF at age < 4 months, and outcomes were overweight (BMI z-score > 85th percentile) and obesity (BMI z-score > 95th percentile) at ages 5-7 years. RESULTS: Of the 154,565 eligible children in the observed cohort, 10,499 (6.8%) were introduced to CF at age < 4 months and 144,066 (93.2%) at age ≥ 4 months. Propensity score matching yielded 9680 children introduced to CF at age < 4 months and 35,396 at age ≥ 4 months. The risk for being overweight or obese at age 5-7 years was slightly higher among those who started CF at age < 4 months than at age ≥4 months (adjusted relative risk = 1.06; 95% confidence interval = 1.02-1.09). A similar but stronger association was observed for being obese at age 5-7 years (adjusted relative risk = 1.12; 95% confidence interval = 1.05-1.19). CONCLUSIONS: Early CF introduction before age 4 months was associated with increased BMI at age 5-7 years.

Neurodevelopmental Outcomes in Infants Fed with Soy Formula: A Retrospective, National Population-Based Observational Cohort Study.

BACKGROUND: Soy-based infant formulas are increasingly popular, but data regarding their effects on neurodevelopmental outcomes during early childhood is scanty. OBJECTIVE: This study investigated the effect of consuming soy-based infant formula at 9-12 mo after birth on the subsequent development of epilepsy, neurodevelopmental disorders, and developmental status. METHODS: This nationwide retrospective administrative study used health screening examinations and linked insurance claims data of children born in Korea during 2008 and 2009. Infants who received soy formula were compared with those who received cow's milk formula using propensity score matching that considered birth history, economic status, clinical conditions, and drug prescription records. Exposure was defined as soy formula feeding determined from questionnaires completed by the parents when children were 9-12 mo old. Outcomes were epilepsy, attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and developmental status. Children were followed until 31 December, 2017. RESULTS: A total of 153,841 eligible participants were enrolled; 11,535 (7.5%) children received soy formula, while 142,864 (92.5%) received cow's milk formula. The incidence rate of epilepsy during the follow-up period was 29.8 per 100,000 person-years (95% CI: 19.48, 41.65) in the soy formula group and 22.6 per 100,000 person-years (95% CI: 31.97, 59.07) in the cow's milk formula group, with no significant difference (aHR: 1.318; 95% CI: 0.825, 2.106). The 2 groups also had no difference based on prespecified analysis using different definitions of epilepsy. Likewise, no significant associations of soy formula with ADHD (aHR: 1.26; 95% CI: 1.00, 1.60) or ASD (aHR: 0.99; 95% CI: 0.54, 1.83), or delays of developmental stages were observed. CONCLUSIONS: Feeding with soy formula rather than cow's milk formula had no apparent association with increased risks of epilepsy, ADHD, ASD, and developmental status, according to this cohort composed of a general pediatric population.