07.29.2013
by Michael Smith North American Correspondent, MedPage Today

Action Points

Longer breastfeeding over the first year of life was linked to better understanding of language at 3 and better verbal and nonverbal intelligence at 7, researchers reported.

Also, any breastfeeding — as opposed to none — was associated with better verbal intelligence at 7, according to Mandy Belfort, MD, of Boston Children’s Hospital, and colleagues.

The findings, from a prospective cohort study, support a causal link between breastfeeding and later intelligence, Belfort and colleagues argued online in JAMA Pediatrics.

Taken with other research, Belfort and colleagues said, the study supports national and international recommendations in favor of exclusive breastfeeding through 6 months and at least some breastfeeding in the rest of the first year.

Indeed, the possible impact on cognition might be the factor that increases breastfeeding in the U.S., commented Dimitri Christakis, MD, of the Seattle Children’s Hospital Research Institute.

In an accompanying editorial, he noted that breastfeeding is known to reduce the incidence of such things as gastroenteritis, otitis media, and atopic eczema, but those outcomes, while desirable, do not have “dramatic public health consequences.”

Children’s cognitive function might be “the force that tilts the scale” and prompts a range of changes in policy and public opinion on breastfeeding, Christakis argued.

He also noted that many women start breastfeeding, but fail to sustain it; after 6 months only 35% of women overall and 20% of black women still breastfeed their infants.

Belfort and colleagues studied 1,312 mothers and children in Project Viva, a study that enrolled pregnant women and followed them and their children until the children were 7.

When children were 3, the researchers measured language understanding with the Peabody Picture Vocabulary Test and motor skills with the Wide Range Assessment of Visual Motor Abilities.

When they were 7, Belfort and colleagues measured verbal and nonverbal intelligence with the Kaufman Brief Intelligence Test, and also looked again at motor skills with the Wide Range Assessment of Visual Motor Abilities.

All the tests have a 100-point scale, where higher scores indicate a better result.

Analysis controlled for such things as age and sex of the children, their health, and socioeconomic factors, as well as maternal intelligence and the home environment.

In a fully adjusted regression analysis, Belfort and colleagues reported, longer breastfeeding was associated with a higher Peabody Picture Vocabulary Test score at age 3 — an increase of 0.21 points per month of breastfeeding.

Longer breastfeeding was also associated with higher intelligence on the Kaufman Brief Intelligence Test at 7 — increases of 0.35 points per month on the verbal scale and 0.29 points per month on the nonverbal scale.

There were no links between breastfeeding and the motor skills test, Belfort and colleagues reported.

Put another way, Christakis commented, breastfeeding an infant for the first year of life would be expected to increase his or her IQ by about 4 points.

Because most other studies have had a dichotomous endpoint — breastfeeding or not — the researchers also analysed their data that way and found that 7-year-old breastfed children scored 3.75 points higher on the Kaufman test than those who were not breastfed.

They were also higher on the Peabody test at 3 but not significantly so.

Belfort and colleagues cautioned that the study was observational, so that unmeasured factors might have affected the outcomes. And, although the main outcomes were statistically significant, the lower bounds of the 95% confidence intervals include “values with little clinical importance,” they noted.

• Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

last updated 07.30.2013