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| Brian Silver, MD |
There is growing evidence that breastfeeding may reduce the risk for stroke in post-menopausal women who reported breastfeeding at least one child, according to new research in the Journal of the American Heart Association, the open access journal of the American Heart Association/American Stroke Association.
The study, co-authored by Brian Silver, MD, the Endowed Chair in Neuroscience Research and vice chair and professor of neurology at UMass Medical School, is among the first to examine breastfeeding and a possible relationship to stroke risk for mothers, as well as how such a relationship might vary by ethnicity. Stroke is the fourth leading cause of death among women aged 65 and older, and is the third leading cause of death among Hispanic and black women aged 65 and older.
Lisette T. Jacobson, PhD, study lead author and assistant professor of preventive medicine and public health at University of Kansas School of Medicine-Wichita, and colleagues analyzed data on 80,191 participants in the Women’s Health Initiative observational study, a large ongoing national study that has tracked the medical events and health habits of postmenopausal women who were recruited between 1993 and 1998. Dr. Silver advised the researchers on the neurological aspects of the study and made recommendations for analyzing confounding factors such as lifestyle and certain risk factors.
All women in this analysis had delivered one or more children and 58 percent reported ever having breastfed. Among the 58 percent of women who had delivered one or more children and who also reported having breastfed, 51 percent breastfed for 1-6 months, 22 percent for 7-12 months and 27 percent for 13 or more months. At the time of recruitment, the average age was 63.7 years and the follow-up period was 12.6 years.
After adjusting for non-modifiable stroke risk factors (such as age and family history), researchers found stroke risk among women who breastfed their babies was on average:
- 23 percent lower in all women,
- 48 percent lower in black women,
- 32 percent lower in Hispanic women,
- 21 percent lower in white women, and
- 19 percent lower in women who had breastfed for up to six months. A longer reported length of breastfeeding was associated with a greater reduction in risk.
“While breastfeeding has many positive immediate benefits for mother and child, that there would be such a strongly significant association with a health outcome much later in life was unanticipated, at least for me,” Silver said. “The linear relationship between duration of breastfeeding and reduction in stroke risk suggests some sort of dose-response relationship though causality is not at all proven in this kind of study.”
“It is also possible that a confounder that was not measurable in the multivariable analysis might have accounted for the relationship e.g. certain characteristics common to both a longer duration of breastfeeding and a lower risk of stroke,” he said.
The study did not address whether racial or ethnic differences in breastfeeding contribute to disparities in stroke risk.
Because the study was observational, it couldn’t establish a cause-and-effect relationship between breastfeeding and lower stroke risk, meaning that it is possible some other characteristic that distinguishes between women who breastfeed and those who don’t is the factor changing the stroke risk. However, because the Women’s Health Initiative is large, researchers were able to adjust for many characteristics, and the effects of breastfeeding remained strong, Dr. Jacobson said.
“Breastfeeding is only one of many factors that could potentially protect against stroke. Others include getting adequate exercise, choosing healthy foods, not smoking and seeking treatment if needed to keep your blood pressure, cholesterol and blood sugar in the normal range,” Dr. Jacobson said.
The study was also limited by the relatively small number of strokes that occurred during the follow-up period (just 3.4 percent of the women experienced a stroke during the study period and 1.6 percent reported having had a stroke prior to the study) and by the Women’s Health Initiative’s exclusion of women who had already had severe strokes at the time of recruitment.
The American Academy of Pediatrics and the World Health Organization recommend exclusive breastfeeding for six months, with continuation of breastfeeding for one year or longer. For babies’ health, the American Heart Association recommends breastfeeding for 12 months with transition to other additional sources of nutrients beginning at about four - six months of age to ensure sufficient micronutrients in the diet.
