Last Updated: 2008-05-05 17:09:43 -0400 (Reuters Health)
NEW YORK (Reuters Health) - Children who are exclusively breastfed for at least 3 months tend to be more cognitively advanced at school age, according to findings from the Promotion of Breastfeeding Intervention Trial (PROBIT).
Although multiple studies have supported the cognitive benefits of breastfeeding, most have been observational in design, Dr. Michael S. Kramer, at McGill University in Montreal, and his associates note in the May Archives of General Psychiatry.
The PROBIT Study was a cluster-randomized trial in which 31 maternal hospitals and affiliated clinics in the Republic of Belarus adopted a program supporting and promoting breastfeeding or continued their current practices and policies. More than 17,000 healthy newborns were enrolled between June 1996 and December 1997.
Significantly more infants born at the intervention hospitals were breastfed at 3 months (72.7% vs 60.0%), and remained so throughout their first year. The rate of exclusive breastfeeding was 7-fold higher in the experimental group at 3 months (43.3% vs 6.4%).
A total of 7108 children in the experimental group and 6781 in the control group were assessed at an average age of 6.5 years.
The Wechsler Abbreviated Scales of Intelligence (WASI) test results showed statistically significantly higher cluster-adjusted mean differences in the experimental intervention group for vocabulary (+4.9), similarities (+4.6), and verbal IQ (+7.5).
Teachers' academic ratings were also significantly higher for reading and writing among the children in the experimental group, Dr. Kramer and his associates report.
WASI scores were superior among children who had been exclusively breastfed and with increased length of breastfeeding, regardless of treatment group, as were teacher ratings for reading, writing, mathematics, and other subjects.
According to the authors, the differences in cognitive development may be due to constituents (such as essential long-chain polyunsaturated fatty acids or insulinlike growth factor I) present at higher concentrations in breast milk than in formula, or they may be related to the physical and social interactions inherent in breastfeeding.
"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," Dr. Kramer's team concludes.
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Arch Gen Psychiatry 2008;65:578-584.