Higher IQ Connected to Breastfeeding

From the Christchurch Health and Development Study, Christchurch
School of Medicine, Christchurch, New Zealand.

Objective.  This study examines the associations between duration of breastfeeding and childhood cognitive ability and academic achievement over the period from 8 to 18 years using data collected during the course of an 18-year longitudinal study of a birth cohort of >1000 New Zealand children.

Method.  During the period from birth to age 1 year, information was collected on maternal breastfeeding practices. Over the period from 8 to 18 years, sample members were assessed on a range of measures of cognitive and academic outcomes including measures of child intelligence quotient; teacher ratings of school performance; standardized tests of reading comprehension, mathematics, and scholastic ability; pass rates in school leaving examinations; and leaving school without qualifications.

Results.  Increasing duration of breastfeeding was associated with consistent and statistically significant increases in 1) intelligence quotient assessed at ages 8 and 9 years; 2) reading comprehension, mathematical ability, and scholastic ability assessed during the period from 10 to 13 years; 3) teacher ratings of reading and mathematics assessed at 8 and 12 years; and 4) higher levels of attainment in school leaving examinations. Children who were breastfed for >= 8 months had mean test scores that were between 0.35 and 0.59 SD units higher than children who were bottle-fed.

Mothers who elected to breastfeed tended to be older; better educated; from upper socioeconomic status families; were in a two-parent family; did not smoke during pregnancy; and experienced above average income and living standards. Additionally, rates of breastfeeding increased with increasing birth weight, and first-born children were more likely to be breastfed.

Regression adjustment for maternal and other factors associated with breastfeeding reduced the associations between breastfeeding and cognitive or educational outcomes. Nonetheless, in 10 of the 12 models, fitted duration of breastfeeding remained a significant predictor of later cognitive or educational outcomes. After adjustment for confounding factors, children who were breastfed for >= 8 months had mean test scores that were between 0.11 and 0.30 SD units higher than those not breastfed.

Conclusions.  It is concluded that breastfeeding is associated with small but detectable increases in child cognitive ability and educational achievement. These effects are 1) pervasive, being reflected in a range of measures including standardized tests, teacher ratings, and academic outcomes in high school; and 2) relatively long-lived, extending throughout childhood into young adulthood. Key words: breastfeeding, cognitive ability, academic achievement, longitudinal study.      _________________________________________________
Copyright 1997 by the American Academy of Pediatrics.
 

Study References.

1)
Pollock, J.I.
"Long-term associations with infant feeding in a clinically advantaged population of babies."
Dev. Med. Child Neurol. 1994; 36(5);429-40
[Some aspects of intellectual attainment at five and ten years of age can be demonstrated to be inferior among children who were formula-fed compared with those that were exclusively breastfed for at least three months.]

2)
Morley R., et al
"Mother's choice to provide breastmilk and developmental outcome."
Arch Dis Child 63:1382-1385, 1988.
[Formula-fed preterm infants had lower Bayley Mental Develpment scores at 18 months, even after adjusting for social and demographic influence.]

3)
Morrow-Tlucak, M, et al.,
"Breastfeeding and cognitive development in the first two years of life."
Soc Sci Med 26:635-639, 1988.
[Scores on the Bayley Mental Development Index were lower in formula-fed at 1-2 years of age, and scores were directly correlated with duration of breastfeeding.]

4)
Bauer G, et al.
"Breastfeeding and cognitive development of three-year-old children."
Psychological Reports 68:1218, 1991.
[Scores on the McCarthy Scales of Children's Abilities were significantly lower at three years of age as the duration of breastfeeding decreased.]

5)
Taylor B, et al.
"Breastfeeding and child development at five years."
Dev Med Child Neurol 26:73-80, 1984.
[Formula-fed children showed reduced performance on developmental tests at age five years.]

6)
Lucas, A. et al.
"Breast milk and subsequent intelligence quotient in children born preterm."
Lancet 1992;33;261-62.
[Formula-fed preterm infants had lower IQ scores at age 7-8 years than preemies fed expressed breastmilk; the association held after controlling for mother's education and social class, and regardless of whether the mother attempted to express milk and failed or never attempted to express milk.]

7)
Lucas, A., et al.
"A randomised multicentre study of human milk versus formula and later development in preterm infants."
Arch. Dis. Child 1994; 70;F141-146




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