Breast-feeding May Up IQ for Toddlers and Grade-schoolers

Diedtra Henderson

July 29, 2013

Infants who had been breast-fed to age 12 months had higher vocabulary scores at 3 years of age and registered higher verbal and nonverbal intelligence scores at 7 years of age compared with nonbreast-fed infants, in a prospective, longitudinal cohort study.

Mandy B. Belfort, MD, MPH, from the Division of Newborn Medicine at Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts, and colleagues reported their findings in an article published online July 29 in JAMA Pediatrics.

From April 22, 1999, to July 31, 2002, the authors enrolled 2128 pregnant women in a prospective, longitudinal cohort study, Project Viva.

The current analysis, included 1312 mothers for whom researchers had information regarding their infant's breast-feeding status at 6 months, breast-feeding duration at 12 months, and cognitive measures at ages 3 and 7 years. The mothers who were excluded were less educated, had lower annual household income, and breast-fed for a shorter duration, according to Dr. Belfort and colleagues.

Longer breast-feeding was associated with higher Peabody Picture Vocabulary Test score at age 3 years (0.21; 95% confidence interval [CI], 0.03 - 0.38 points per month breast-fed) in adjusted linear regression analysis, as well as with higher intelligence on the Kaufman Brief Intelligence Test at age 7 years (0.35; 95% CI, 0.16 - 0.53 verbal points per month breast-fed; 0.29; 95% CI, 0.05 - 0.54 nonverbal points per month breast-fed). The researchers adjusted for maternal intelligence, sociodemographics, and home environment, using data from self-administered questionnaires, interviews, and home observations with the Home Observation Measurement of the Environment short form.

"We found that longer duration of breastfeeding and greater exclusivity of breastfeeding were associated with better receptive language at age 3 years and with higher verbal and nonverbal IQ at age 7 years," the authors write. "At age 7 years, the effect size of 0.35 verbal IQ points per month of any breastfeeding translates to 4.2 points, or almost one-third of [a standard deviation] during 12 months, whereas the effect size of 0.80 verbal IQ points per month of exclusive breastfeeding translates to almost 5 points over 6 months," the researchers continue.

Dimitri A. Christakis, MD, MPH, from the Seattle Children's Research Institute, Washington, says in an accompanying editorial that among its "many notable strengths," the study controlled for maternal intelligence and features of the home environment that promote cognitive function. Earlier observational studies did not adjust for such variables, muddying the results.

However, noting that the World Health Organization and the American Academy of Pediatrics already endorse breast-feeding, Dr. Christakis expressed doubt that the IQ results alone would dramatically improve public health.

"Merely reiterating the importance of breastfeeding is clearly not enough; another call for action is not enough either, instead, real action is in order," he writes. Meaningful reduction in childhood exposure to lead came after Congressional legislation, national public service announcements, and routine lead screening.

"An analogous large, robust, and sustained effort is needed to provide the infrastructure to support breastfeeding at all levels," according to Dr. Christakis.

Although 70% of American women initiate breast-feeding, the proportion drops to 35% by 6 months, according to the editorial.

The study authors argue that the IQ boost is a reason for infants to be exclusively breast-fed for the first months of life. "[O]ur results support a causal relationship of breastfeeding in infancy with receptive language at age 3 and with verbal and nonverbal IQ at school age," Dr. Belfort and colleagues conclude. "These findings support national and international recommendations to promote exclusive breastfeeding through age 6 months and continuation of breastfeeding through at least age 1 year."

Support for this study was provided by the National Institutes of Health. The study authors have disclosed no relevant financial relationships. The editorialist disclosed being cochair of the Excellence in Paediatrics Global Breastfeeding Initiative.

JAMA Pediatr. Published online July 29, 2013.

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