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

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.


Overall representativeness of this study
We used a large representative sample (1.61 million children) and sophisticated statistical techniques to strengthen and generalize our main findings.This is largest analysis to evaluate protective breastfeeding effect of subsequent hospital admission and first analysis to focus on the lag time effect of subsequent hospital admission.We should determine whether the effect differs depending on when the individuals were born.Within each cohort, we compared the incidence rates of the primary outcome on those who were followed up for various periods (calendar period of birth).a Hospital admission rate is expressed as per 100 person-years.
We performed the negative binomial regression model (endpoint, incidence rate of any hospital admission) with incidence rate ratios and 95% CIs.
Numbers in bold indicate significant differences (two sided p < 0.05).a Hospital admission rate is expressed as per 100 person-years.
We performed the negative binomial regression model (endpoint, incidence rate of any hospital admission) with incidence rate ratios and 95% CIs.
Numbers in bold indicate significant differences (two sided p < 0.05).IRR incidence rate ratio, CI confidence interval.
We performed the negative binomial regression model (endpoint, incidence rate of any hospital admission) with incidence rate ratios and 95% CIs.
Numbers in bold indicate significant differences (two sided p < 0.05).IRR incidence rate ratio, CI confidence interval.
We performed the negative binomial regression model (endpoint, incidence rate of any hospital admission) with incidence rate ratios and 95% CIs.
Numbers in bold indicate significant differences (two sided p < 0.05).a Give information separately for cases and controls in case-control studies and, if applicable, for exposed and unexposed groups in cohort and cross-sectional studies.

.770 (0.715 to 0.829) 0.814 (0.737 to 0.899) 0.739 (0.655 to 0.834)
0.910 (0.787 to 1.052) 0.866 (0.730 to 1.027) Give characteristics of study participants(e.g., demographic, clinical, social)and information on exposures and potential confounders P8-9 Results (b) Indicate number of participants with missing data for each variable of interest P8-9 Results (c) Cohort study-Summarise follow-up time (e.g., average and total amount) Cohort study-Report numbers of outcome events or summary measures over time P8-9 Results Case-control study-Report numbers in each exposure category, or summary measures of exposure Cross-sectional study-Report numbers of outcome events or summary measures Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (e.g., 95% confidence interval).Make clear which confounders were adjusted for and why they were included Funding 22 Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based P22 Funding An Explanation and Elaboration article discusses each checklist item and gives methodological background and published examples of transparent reporting.The STROBE checklist is best used in conjunction with this article (freely available on the web sites of PLoS Medicine at http://www.plosmedicine.org/,Annals of Internal Medicine at http://www.annals.org/,and Epidemiology at http://www.epidem.com/).Information on the STROBE initiative is available at www.strobe-statement.org.