Breastfeeding positively associated with intelligence, educational attainment, and income at 30 years

1. Total duration of breastfeeding in infancy was positively associated with intelligence, education level, and income at 30 years of age.

2. Findings suggested that breastfeeding had long-lasting impacts into adulthood with important real-life implications by increasing education and income potentials.

Evidence Rating Level: 2 (Good)

Study Rundown: The biological health benefits of breastfeeding are well known, but the long-term benefits are less clear. This prospective cohort study aimed to assess the long-term benefits of breastfeeding by following 3,493 Brazilians from shortly after birth into adulthood 30 years later. Associations between breastfeeding duration and intelligence quotient (IQ), years of schooling, and income at 30 years of age were measured in a setting where strong social patterning of breastfeeding was not prevalent. For all analyses, breastfeeding positively correlated with IQ, education attainment, and income. Adjustment for ten potential confounders of the relationship led to a near-linear association between breastfeeding and the measured outcomes. These results suggest that breastfeeding holds not only its currently known short-term benefits, but has long-term impacts both on the individual and societal level, by increasing educational attainment and income generation. The high follow up rate is a major strength of this study. Because IQ is positively associated with socioeconomic position, residual confounding by socioeconomic status must be considered when assessing these findings.

The study was funded by Wellcome Trust, International Development Research Center (Canada), CNPq, FAPERGS, and the Brazilian Ministry of Health.

Click to read the study in The Lancet Global Health

Relevant Reading: Is breast truly best? Estimating the effects of breastfeeding on long-term child health and wellbeing in the United States using sibling comparisons

In-Depth [prospective cohort]: This study aimed to assess the relationship between breastfeeding in infancy and long-term benefits in terms of intelligence, educational attainment, and income in adulthood. 3,493 infants in Pelotas, Brazil were followed from infancy in 1982 to 30 years of age in 2013. IQ was measured by administration of the Wechsler Adult Intelligence Scale, 3^rd version at a mean age of 30.2 years. Educational attainment was categorized by the highest grade successfully completed by the participant. Income was recorded by previous month’s earnings in Brazilian reals (R$). In 2012, US$1 was equivalent to 0.49 real in 2012. Ten confounding variables were taken into account for this analysis and controlled for, including maternal education, family income, maternal smoking during pregnancy, maternal age, type of delivery, maternal pre-pregnancy body-mass index, gestational age, and birth weight.

For IQ and educational attainment, dose-response associations were identified. In a confounder-adjusted analysis, participants who were breastfed for at least 12 months had higher IQ scores (difference of 3.76 points, 95%CI 2.20-5.33), more years of education (0.91 years, 95%CI 0.42-1.40), as well as greater monthly income (341.0 R$, 93.8-588.3) than those who were breastfed for less than one month. Correlation coefficients were 0.42 (p < 0.0001) between income and IQ, and 0.39 (p < 0.0001) between income and education.

Image: PD

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