Influence of breastfeeding on cognitive outcomes at age 6-8 years: follow-up of very low birth weight infants.

The relation between breastfeeding and childhood cognitive development was examined in 1991-1993 among 439 school-age children weighing <1,500 g when born in the United States between 1991 and 1993. Measures of cognitive function included overall intellectual function, verbal ability, visual-spatial and visual-motor skill, and memory. Higher test scores for each domain of cognitive function except memory were observed among children who were breastfed directly. After covariate adjustment for home environment, maternal verbal ability, a composite measure of parental education and occupation, and length of hospitalization, the authors found that breastfed children evidenced an advantage only for measures specific to visual-motor integration (5.1 intelligence quotient (IQ) points, 95% confidence interval: 1.0, 9.2). Differences in test scores between breastfed children and those who did not receive any breast milk feedings were 3.6 IQ points (95% confidence interval: -0.3, 7.5) for overall intellectual functioning and 2.3 IQ points (95% confidence interval: -3.0, 7.6) for verbal ability. Indicators of social advantage confound the association between breastfeeding and cognitive function, but careful measurement can reduce residual confounding and may clarify causal relations.