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 ofArchives 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.