Breast feeding and infant development in a cohort with sibling pair analysis: the Japan Environment and Children's
Masafumi Sanefuji1,2, Ayako Senju3,4, Masayuki Shimono3,4
1Research Center for Environment and Developmental Medical Sciences, Kyushu University, Fukuoka, Japan sanefuji39@gmail.com.
Insights
Continued breastfeeding is linked to better infant development. This study found breastfeeding until 12 months reduced developmental delays at one year, even after accounting for family factors.
Area of Science:
- Pediatrics
- Developmental Psychology
- Public Health
Background:
- Breastfeeding is widely recommended for infant health.
- Understanding its long-term impact on development is crucial.
- Sibling studies help control for genetic and environmental factors.
Purpose of the Study:
- To examine the association between breastfeeding and infant development.
- To assess developmental delay at 6 and 12 months of age.
- To utilize sibling comparison to minimize confounding variables.
Main Methods:
- Prospective birth cohort study including over 77,000 children.
- Developmental delay assessed using the Ages and Stages Questionnaires.
- Sibling pair analysis and multivariable regression were employed.
Main Results:
- Breastfeeding until 6 or 12 months was associated with reduced developmental delay at 12 months.
- Exclusive breastfeeding until 3 months also showed reduced delay.
- Sibling analysis confirmed the association between breastfeeding until 12 months and reduced delay.
Conclusions:
- Continuous breastfeeding is associated with reduced developmental delay at one year.
- Sibling pair analysis strengthens these findings by reducing unmeasured confounding.
- Results support the promotion of breastfeeding continuation.
Objectives:
To investigate the association between breast feeding and infant development during the first year of life using sibling comparison.
Design:
Nationwide prospective birth cohort study with sibling pair analysis.
Setting:
15 regional centres that participated in the Japan Environment and Children's Study.
Participants:
This study included 77 119 children (singleton, term birth and no malformation/severe diseases) whose mothers were registered between January 2011 and March 2014, including 3521 duos or trios of siblings.
Primary Outcome Measures:
The primary outcome was developmental delay at 6 and 12 months of age, assessed using the Japanese translation of the Ages and Stages Questionnaires, third edition. Multivariable regression analyses adjusted for confounders were performed to estimate the risk ratios of delay associated with any or exclusive breast feeding. Pairs of siblings discordant for statuses were selected, and conditional regression analyses were conducted with a matched cohort design.
Results:
Developmental delay was identified in 6162 (8.4%) and 10 442 (14.6%) children at 6 and 12 months of age, respectively. Any breast feeding continued until 6 months or 12 months old was associated with reduced developmental delay at 12 months of age (adjusted risk ratio (95% CI): 0.81 (0.77 to 0.85) and 0.81 (0.78 to 0.84), respectively). Furthermore, exclusive breast feeding until 3 months was associated with reduced developmental delay at 12 months of age (adjusted risk ratio, 0.86 (95% CI 0.83 to 0.90)). In sibling pair analysis, the association between any breast feeding until 12 months and reduced developmental delay at 12 months of age persisted (adjusted risk ratio, 0.64 (95% CI 0.43 to 0.93)).
Conclusions:
The present study demonstrated the association of continuous breast feeding with reduced developmental delay at 1 year of age using sibling pair analysis, in which unmeasured confounding factors are still present but less included. This may provide an argument to promote breastfeeding continuation.
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