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Prolonged, Exclusive Breast-Feeding Linked to Improved Cognitive Development

  • Authors: News Author: Laurie Barclay, MD
    CME Author: Désirée Lie, MD, MSEd
  • CME/CE Released: 5/6/2008
  • Valid for credit through: 5/6/2009
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Target Audience and Goal Statement

This article is intended for primary care clinicians, obstetricians, and other specialists who care for infants.

The goal of this activity is to provide medical news to primary care clinicians and other healthcare professionals in order to enhance patient care.

Upon completion of this activity, participants will be able to:

  1. Describe the association between infant breast-feeding and Wechsler Abbreviated Scales of Intelligence scores in children aged 6.5 years.
  2. Describe the association between infant breast-feeding and teacher evaluations of academic performance of children at 6.5 years and the dose-response association between breast-feeding and cognitive development in children.


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  • Laurie Barclay, MD

    Laurie Barclay, MD, is a freelance reviewer and writer for Medscape.


    Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.


  • Brande Nicole Martin

    Brande Nicole Martin is the News CME editor for Medscape Medical News.


    Disclosure: Brande Nicole Martin has disclosed no relevant financial information.

CME Author(s)

  • Désirée Lie, MD, MSEd

    Clinical Professor, Family Medicine, University of California, Orange; Director, Division of Faculty Development, UCI Medical Center, Orange, California


    Disclosure: Désirée Lie, MD, MSEd, has disclosed no relevant financial relationships.

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Prolonged, Exclusive Breast-Feeding Linked to Improved Cognitive Development

Authors: News Author: Laurie Barclay, MD CME Author: Désirée Lie, MD, MSEdFaculty and Disclosures

CME/CE Released: 5/6/2008

Valid for credit through: 5/6/2009


May 6, 2008 — Prolonged and exclusive breast-feeding improves cognitive development as measured by IQ and teachers' academic ratings in children at age 6.5 years, according to the results of the largest randomized trial ever conducted in the area of human lactation, published in the May issue of Archives of General Psychiatry.

"The evidence that breastfeeding improves cognitive development is based almost entirely on observational studies and is thus prone to confounding by subtle behavioral differences in the breastfeeding mother’s behavior or her interaction with the infant," write Michael S. Kramer, MD, and colleagues from the Promotion of Breastfeeding Intervention Trial (PROBIT) Study Group.

The goal of this cluster-randomized trial was to determine whether prolonged and exclusive breast-feeding was associated with improved cognitive ability in children at age 6.5 years. At 31 Belarussian maternity hospitals and their affiliated polyclinics, 17,046 healthy breast-feeding infants were enrolled from June 17, 1996, to December 31, 1997, and 13,889 of these infants (81.5%) were followed up from December 21, 2002, to April 27, 2005, at age 6.5 years.

The breast-feeding promotion intervention was modeled on the Baby-Friendly Hospital Initiative by the World Health Organization and United Nations Children's Fund (UNICEF). Primary outcomes were subtest and IQ scores on the Wechsler Abbreviated Scales of Intelligence (WASI), and teacher evaluations of academic performance in reading, writing, mathematics, and other subjects.

Compared with the control group, the intervention group had a large increase in exclusive breast-feeding at age 3 months (43.3% vs 6.4%; P < .001) and a significantly higher prevalence of any breast-feeding at all ages, up to and including 12 months.

Compared with the control group, the intervention group had higher means on all of the WASI measures. Cluster-adjusted mean differences were +7.5 (95% confidence interval [CI], 0.8 - 14.3) for verbal IQ, +2.9 (95% CI, −3.3 to +9.1) for performance IQ, and +5.9 (95% CI, −1.0 to +12.8) for full-scale IQ. For both reading and writing, teachers' academic ratings were significantly higher in the experimental group.

"These results, based on the largest randomized trial ever conducted in the area of human lactation, provide strong evidence that prolonged and exclusive breastfeeding improves children’s cognitive development," the study authors write.

The major study limitation is lack of blinding of the pediatricians who administered the WASI to the experimental vs control intervention status of the children they examined.

"Because protection against infections in developed country settings does not have the life-and-death implications for infant and child health that it does in less-developed settings, cognitive benefits may be among the most important advantages for breastfed infants in industrialized societies," the study authors write. "The consistency of our findings based on a randomized trial with those reported in previous observational studies should prove helpful in encouraging further public health efforts to promote, protect, and support breastfeeding."

The Canadian Institutes of Health Research supported this study. The authors have disclosed no relevant financial relationships.

Arch Gen Psychiatry. 2008;65:578-584.

Clinical Context

Observational studies of breast-feeding have consistently demonstrated a positive effect of breast-feeding on infant cognitive development using IQ measures compared with formula-feeding and a dose-response association with larger differences for longer duration of breast-feeding. Randomization to breast-feeding vs formula-feeding is unfeasible, but randomization to a strategy to promote breast-feeding among mothers who have already decided to initiate breast-feeding can be performed.

PROBIT is the largest randomized trial of human lactation ever conducted and used a cluster randomization design to randomize hospitals and clinics in Belarus to an intervention to promote breast-feeding using the Baby-Friendly Hospital Initiative of WHO and UNICEF. In this study, the WASI IQ measures and teacher evaluations of academic performance in children at 6.5 years were linked to breast-feeding in infancy.

Study Highlights

  • Included were participants in the PROBIT study consisting of 17,046 healthy term infants weighing at least 2500 g at birth, from 31 maternity hospitals and their associated polyclinics in 1 country.
  • Sites were randomized to either an intervention to promote breast-feeding or usual policy.
  • The 2 types of cluster groups were matched for maternal age, education, previous breast-feeding, and number of other children.
  • The experimental intervention led to a significant increase in duration of any breast-feeding up to 12 months and also of exclusive breast-feeding up to 6 months.
  • Follow-up interviews and examinations were conducted at 6.5 years by pediatricians, 1 to 2 for each site, using the WASI scale.
  • The WASI consisted of 4 subsets testing vocabulary, similarities, block design, and matrices and took 30 minutes to administer.
  • It was translated to Russian and back translated to ensure comparability of the Russian version.
  • Children who had begun school by the 6.5 year follow-up were evaluated by their teachers in 4 components: reading, writing, mathematics, and other subjects.
  • The child was rated using a 5-point scale as "far below," "somewhat below," "at somewhat above," or "far above" his or her grade level.
  • 5 children were randomly selected for audit for each pediatrician to assess inter-rater reliability and consistency of WASI testing.
  • More than 80% of mothers were aged 20 to 34 years, half had completed secondary education, more than half had no other children at home, and fewer than 3% smoked during pregnancy.
  • Mean birth weight was 3440 g.
  • The 2 randomized groups were similar in demographics.
  • Follow-up at 6.5 years was 81.5% with similar rates in the 2 groups.
  • The cluster-adjusted mean difference in IQ was greatest for verbal IQ.
  • The verbal IQ was +7.5 points higher; the performance IQ, +2.9 points higher; and the full-scale IQ, +5.9 points higher in the breast-feeding intervention vs the no intervention group.
  • The results of the WASI demonstrated a high degree of clustering and large confidence intervals.
  • After adjusting for the cluster randomization, differences in mean scores for the WASI were +2.8 for verbal IQ, +2.9 for performance IQ, and +3.1 for full-scale IQ.
  • After carrying out sensitivity analyses to account for the large site variations, the differences were +4.7, +4.0, and +4.9, respectively.
  • There was a slightly greater mean difference in verbal IQ for boys (8 points higher for boys and 7 points higher for girls) in the breast-feeding vs the control group.
  • Higher WASI scores were seen with greater duration of breast-feeding and of exclusive breast-feeding.
  • Exclusive breast-feeding for 6 months or more was associated with an increase in verbal IQ score of +5.2 points vs exclusive breast-feeding for less than 3 months.
  • Similar dose-response associations were seen for teacher ratings for all 4 subject areas, but the increases were not significant for breast-feeding duration of 6 months or more.
  • The findings were robust in the direction of benefit for breast-feeding.
  • The authors concluded that breast-feeding improved children’s cognitive development.

Pearls for Practice

  • A breast-feeding intervention vs no intervention is associated with higher WASI IQ scores, which are greater for verbal IQ but also indicated for the performance and overall IQ scores, in children age 6.5 years old.
  • Improved IQ scores and teacher evaluations for 6.5-year-old children associated with increased breast-feeding are greater with longer duration of exclusive breast-feeding.