Sibling Comparisons Revise Long-Term Effects of Breast-Feeding

April 8, 2014

Sibling Comparisons Revise Long-Term Effects of Breast-Feeding

  1. Cornelius W. Van Niel, MD

Comparison of siblings who were and were not breast-fed shows no long-term benefit from breast-feeding on measures of obesity and some behavioral and academic outcomes.

  1. Cornelius W. Van Niel, MD

Sociologists have been studying the hypothesis that the long-term superiority of breast-feeding could be due to socioeconomic factors and disparities between mothers and children who do and do not breast-feed, rather than from breast-feeding itself. To examine this possibility and account for unmeasured differences that might affect outcomes, researchers used longitudinal data collected between 1986 and 2010 to compare outcomes in a subset of 1773 siblings (mean age, 9 years) from families with one child who breast-fed and one who did not.

In the full sample of 8237 children, children who were breast-fed had significantly better measures of body mass index, obesity, hyperactivity, parental attachment, vocabulary, reading, math, Wechsler Intelligence Scale, and self-reported scholastic competence, in analysis that controlled for known maternal, prenatal, and birth factors. Similar differences were found in analyses of breast-feeding duration and in children who had ever breast-fed. Interestingly, asthma was significantly more common in breast-fed children. The outcome of behavioral compliance (following household rules) was similar in breast-fed and non–breast-fed groups. However, in analysis of the sibling subgroup, all outcome measures were similar between breast-fed children and their non–breast-fed siblings.


This clever natural comparison of siblings who were and were not breast-fed — and presumably shared similar genetic and environmental factors –– suggests that the benefits of breast-feeding on long-term outcomes related to obesity, behavior, and academics might not be as great as previously thought. The findings do not disprove the short-term benefits of breast-feeding in infants (e.g., reduced ear infections and gastroenteritis, and possibly SIDS risk) or long-term benefits in women of cancer and cardiovascular risk reduction. The authors conclude that breastfeeding can be an economic “sacrifice” and might have less long-term benefit than previously thought. Breast-feeding remains a recommended choice for women for many reasons, but women who cannot or choose not to breast-feed should not feel that their children are destined for inferior outcomes.

Editor Disclosures at Time of Publication

  • Disclosures for Cornelius W. Van Niel, MD at time of publication Equity Covidien; Express Scripts; Johnson & Johnson; Merck


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