Objective: We investigated the relation between duration of breast-feeding in infancy and the intelligence quotient (IQ) of children at 4 y of age in a well-nourished population of an industrialized country.
Methods: Data on duration of breast-feeding were collected prospectively from a cohort of 302 children born between 1998 and 1999 in Adelaide, Australia. The IQ of the children was assessed at 4 y of age using the Stanford-Binet Intelligence Scale. Information on important predictors of childhood IQ including the quality of the home environment was also collected prospectively. Regression analyses were conducted to examine the effect of duration of breast-feeding on IQ with adjustment for potential confounders.
Results: There was no association between the duration of breast-feeding and IQ of the children. The expected IQ of a child at 4 y of age who was breast-fed for 6 mo was only 0.2 point (95% confidence interval -0.8 to 1.2) higher than that of a child who had never been breast-fed after adjustments for the quality of the home environment and socioeconomic characteristics of families using multivariable regression analysis. The quality of the home environment, as assessed by the Home Screening Questionnaire, was the strongest predictor of IQ at 4 y.
Conclusion: There was no association between duration of breast-feeding and childhood IQ in this relatively well-nourished cohort from an industrialized society. In such settings, the apparent benefit of breast-feeding on cognitive function is most likely attributable to sociodemographic factors.