Lykke, E., Michaelsen, K., et al. (2002) The Association Between
Duration of Breastfeeding and Adult Intelligence. JAMA: Vol. 287, No. 18.
Context. A number of
studies suggest a positive association between breastfeeding and
cognitive development in early and middle childhood. However, the only
previous study that investigated the relationship between breastfeeding
and intelligence in adults had several methodological shortcomings.
determine the association between duration of infant breastfeeding and
intelligence in young adulthood.
Design, Setting, and
Participants. Prospective longitudinal birth cohort study
conducted in a sample of 973 men and women and a sample of 2280 men,
all of whom were born in Copenhagen, Denmark, between October 1959 and
December 1961. The samples were divided into 5 categories based on
duration of breastfeeding, as assessed by physician interview with
mothers at a 1-year examination.
Measures Intelligence, assessed using the Wechsler Adult
Intelligence Scale (WAIS) at a mean age of 27.2 years in the mixed-sex
sample and the Børge Priens Prøve (BPP) test at a mean
age of 18.7 years in the all-male sample. Thirteen potential
confounders were included as covariates: parental social status and
education; single mother status; mother's height, age, and weight gain
during pregnancy and cigarette consumption during the third trimester;
number of pregnancies; estimated gestational age; birth weight; birth
length; and indexes of pregnancy and delivery complications.
of breastfeeding was associated with significantly higher scores on the
Verbal, Performance, and Full Scale WAIS IQs. With regression
adjustment for potential confounding factors, the mean Full Scale WAIS
IQs were 99.4, 101.7, 102.3, 106.0, and 104.0 for breastfeeding
durations of less than 1 month, 2 to 3 months, 4 to 6 months, 7 to 9
months, and more than 9 months, respectively (P = .003 for overall F
test). The corresponding mean scores on the BPP were 38.0, 39.2, 39.9,
40.1, and 40.1 (P = .01 for overall F test).
Independent of a wide range of possible confounding factors, a
significant positive association between duration of breastfeeding and
intelligence was observed in 2 independent samples of young adults,
assessed with 2 different intelligence tests.
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