Breastfeeding and impact on childhood hospital admissions: a nationwide birth cohort in South Korea

Abstract

Benefits of breastfeeding for both the mother and the child are well established, but a comprehensive and robust study to investigate the protective effect of breastfeeding and attenuated time effect stratified by cause of morbidity are lacking. This study is based on the nationwide birth cohort in Korea that includes data on all infants born from 2009 to 2015. Of 1,608,540 children, the median follow-up period was 8.41 years (interquartile range, 6.76-10.06). When compared to children with fully formula feeding, the hospital admission rate was 12% lower in those with partially breastfeeding and 15% lower in those with exclusive breastfeeding. The apparent protective effect of breastfeeding was reduced with increasing age. Our study provides potential evidence of the beneficial association of breastfeeding on subsequent hospital admissions. The protective effect declined over time as the children grew older. Encouraging any breastfeeding for at least the first 6 months among infants is an important public health strategy to improve overall child health.

Fig. 1. Diagrammatic representation of Korean nationwide birth cohort before and after propensity matching.

Total 1,608,540 participants born in South Korea between 2009 and 2015 were included. According to the types of infant feeding, they were categorized in three groups: exclusive breastfeeding, partially breastfeeding, and fully formula feeding. Propensity scores were derived using a multivariable logistic regression model from the predicted probability of exclusively breastfed infants vs. fully formula-fed infants (each n = 600,988).

Fig. 2. Flow chart of study enrollment.

Among 2,010,325 infants, 401,785 infants were excluded and 1,608,540 infants were included. The observation period was between 1 January 2009 and 31 December 2019.

Fig. 3. Incidence rate ratio of hospital admissions by types of infant feeding, stratified by age at admission and cause of morbidity.

(A) infection and gastrointestinal tract; (B) respiratory and genitourinary tract; and (C) oral cavity, mental health, and injury/external. Incidence rate ratio (blue circle and red square dots) with 95% CI (error bar) for key causes of infection, gastrointestinal tract, respiratory, genitourinary tract, oral cavity, mental health, and injury/external. We performed the negative binomial regression model (endpoint, incidence rate of any hospital admission) with incidence rate ratios and 95% CIs. Models were adjusted for infant sex, calendar period of birth (2009−2010, 2011−2012, and 2013−2015), birth season (spring, summer, autumn, or winter), region of residence (rural or urban), household income (high, middle, or low), preterm birth (≤36 weeks), and low birth weight (≤2499 g). Numbers in bold indicate significant differences (two-sided p < 0.05).CI confidence interval. Source data are provided as a Source Data file.