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.

BackgroundPrevious studies have argued that attention deficit hyperactivity disorder (ADHD) is associated with asthma. However, reliable evidence to verify this association has not yet been reported.ObjectivesTo investigate the bidirectional association between asthma and ADHD through a 12-year big data cohort study.MethodsThe independent variable group was extracted from 3.5 million individuals randomly sampled by the National Health Insurance Service (NHIS). In Study 1, the incidence of ADHD according to asthma was evaluated, while in Study 2, the incidence of asthma according to ADHD was analyzed. Propensity score (PS) matching with several variables was used to obtain a control group.Measurements and main resultsIn Study 1, the asthma group included 131,937 individuals and the non-asthma group included 131,937 individuals. The adjusted hazard ratio (aHR) for ADHD in the asthma group was 1.17 [95% confidence interval (CI): 1.11–1.23]. In subgroup analysis, the aHRs for ADHD of individuals in the subgroups male sex, 0–5 years old, 6–10 years old, atopic dermatitis, allergic rhinitis, Charlson comorbidity index (CCI) 1, and CCI > 2 were significant (aHR: 2.83, 1.70, 1.79, 1.09, 1.15, 1.06, and 1.49, respectively). In Study 2, ADHD was found to significantly affect asthma in all age groups (aHRs of the subgroups 0∼60 and 0∼17 years old were 1.10 and 1.09, respectively). In the 0∼17 years old subgroup, the association of ADHD with asthma was greater with younger age (aHRs of the subgroups 0∼5 and 6∼10 years old were 2.53 and 1.54, respectively).ConclusionFrom long-term follow-up, the incidence of ADHD was 1.17 times higher in the asthma group than in the control group. The incidence of asthma was 1.10 times higher in the ADHD group than in the control group. Asthma and ADHD have a bidirectional relationship, and childhood asthma and ADHD should be rigorously managed.

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