Written by: Sandeep Ravindran, Ph.D. | Issue # 82 | 2019
- Stroke is a major cause of death among US women aged 65 and older, particularly among Hispanic and non-Hispanic black women.
- Breastfeeding may protect against stroke, and a new study investigated the association between breastfeeding and stroke and how it differs by race and ethnicity.
- The study found that breastfeeding was associated with a lower risk of stroke among postmenopausal women, and this association was strongest for non-Hispanic black women.
Stroke is a leading cause of death in US women aged 65 and older [1,2]. It is particularly deadly among Hispanic and non-Hispanic black women, due to their increased rates of risk factors such as hypertension, obesity, and diabetes compared with non-Hispanic white women [3-6].
One factor that may protect against stroke is breastfeeding. Breastfeeding is known to have protective effects on maternal health, such as a reduced risk of breast and ovarian cancer, reduced likelihood of hypertension and diabetes, improved cardiovascular health, and reduced maternal postpartum weight [7-22].
“It looks like breastfeeding has really important effects on the ways mothers recover from pregnancy,” says Professor Eleanor Schwarz at the University of California, Davis, who has also written a commentary on breastfeeding and maternal cardiovascular health . “Moms who are not able to breastfeed end up with higher blood pressure and more risk of diabetes that requires treatment, and both of those factors affect vascular disease, whether that’s heart attacks or strokes or other changes in the blood vessels,” she says.
Both the American Academy of Pediatrics and the World Health Organization recommend exclusive breastfeeding for 6 months, and continuation of breastfeeding for 1 year or longer [24,25]. However, exclusive breastfeeding rates are relatively low in US women, and even more so among Hispanic and non-Hispanic black women [26-29].
“The fact that we do have these very dramatic disparities in the rates of breastfeeding is actually a really big issue, and not everybody makes the links to the longer-term health consequences both for mothers and for infants,” says Schwarz.
Hispanic and non-Hispanic black women have lower breastfeeding rates and are at higher risk for stroke compared with non-Hispanic white women, suggesting that there might be a link between breastfeeding and stroke. However, there have so far been few studies examining the association between breastfeeding and stroke and whether this association differs by race and ethnicity. “I think that where breastfeeding fits in understanding multiple health disparities is a really important piece of the story,” says Schwarz.
A new study by Professor Lisette Jacobson of the University of Kansas School of Medicine addressed whether breastfeeding might protect against stroke, and whether its effects differ by race and ethnicity . Jacobson and her colleagues found that breastfeeding was associated with a lower risk of stroke among postmenopausal women, and this association was strongest for non-Hispanic black women.
The new study analyzed data from a large racially and ethnically diverse cohort of women who participated in the Women’s Health Initiative, a longitudinal national health study that focused on strategies to prevent chronic disease in postmenopausal women [31-34].
The researchers found that after adjusting for multiple stroke risk factors and lifestyle variables, women who reported ever breastfeeding had a 23% lower risk of stroke compared with women who had never breastfed. This association was strongest for non-Hispanic black women.
In addition, breastfeeding for even a relatively short duration of one to six months was associated with a 19% lower risk of stroke, and this association became stronger as breastfeeding duration increased. Longer duration of breastfeeding was associated with a lower risk of stroke in all women studied and among non-Hispanic white and non-Hispanic black women.
“All of that to me is very consistent with the prior literature,” says Schwarz. “I think it’s understood that breastfeeding affects risks of high blood pressure and high sugars, and those are two things that are bad for women’s vasculature,” she says. “It does seem that moms who aren’t able to breastfeed are at greater risk,” says Schwarz.
The researchers point out that their study did not establish a causal relationship between breastfeeding and the risk of stroke, but they found that the association between the two remained statistically significant even after adjusting for various confounding factors.
The researchers conclude that breastfeeding is associated with a lower stroke risk among postmenopausal women, and they suggest that promoting breastfeeding along with other healthy lifestyle behaviors could be helpful in mitigating the risk of stroke. Given that stroke is one of the leading causes of death among Hispanic and non-Hispanic black women, and these populations also experience low breastfeeding rates, the researchers suggest that increasing breastfeeding duration among these women may be particularly beneficial in helping to guard against stroke.
“The challenge is that breastfeeding is a very time-sensitive health behavior,” says Schwarz. “It does appear to have lifelong effects for both women and their babies, but to some extent there’s no point in talking about it once a woman’s milk has dried up, really all we can know at that point is that perhaps she’s at higher risk and we need to modify her other risk factors as best we can,” she says.
The researchers recommend follow-up studies to confirm the epidemiologic evidence that breastfeeding positively influences the risk of chronic diseases such as stroke, and to assess dose-response relationships. Understanding the risk factors for stroke may help researchers develop intervention programs to reduce stroke risk, particularly in populations that are most at risk.
“There’s many, many reasons that we already know that breastfeeding is good for mothers and babies, and so I think really where we need to focus our energies is how to support mothers who want to breastfeed in doing so,” says Schwarz. “Some of that has to do with things like paid maternity leave, so probably changes such as those would have the biggest effect on our public health,” she says.
1. Centers for Disease Control and Prevention. National Center for Health Statistics. Deaths, percent of total deaths, and death rates for the 15 leading causes of death in selected age groups, by race and sex. United States, 2014. Available at: http://www.cdc.gov/nchs/nvss/mortality/lcwk3.htm. Updated September 29, 2017. Accessed November 13, 2018.
2. Heron M. Deaths: leading causes for 2013. National vital statistics reports. Vol 65. Hyattsville, MD; National Center for Health Statistics; 2016.
3. Mozaffarian D., Benjamin E.J., Go A.S., Arnett D.K., Blaha M.J., Cushman M., de Ferranti S., Després J.P., Fullerton H.J., Howard V.J., Huffman M.D., Judd S.E., Kissela B.M., Lackland D.T., Lichtman J.H., Lisabeth L.D., Liu S., Mackey R.H., Matchar D.B., McGuire D.K., Mohler E.R. 3rd, Moy C.S., Muntner P., Mussolino M.E, Nasir K., Neumar R.W., Nichol G., Palaniappan L., Pandey D.K., Reeves M.J., Rodriguez C.J., Sorlie P.D., Stein J., Towfighi A., Turan T.N., Virani S.S., Willey J.Z., Woo D., Yeh R.W., Turner M.B.; American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Heart disease and stroke statistics-2015 update: a report from the American Heart Association. Circulation. 2015 Jan 27;131(4):e29-322.
4. Ogden C.L., Carroll M.D., Fryar C.D., Flegal K.M. Prevalence of Obesity Among Adults and Youth: United States, 2011-2014. NCHS Data Brief. 2015 Nov;(219):1-8.
5. Hayes D.K., Denny C.H., Keenan N.L., Croft J.B., Sundaram A.A., Greenlund K.J. Racial/ethnic and socioeconomic differences in multiple risk factors for heart disease and stroke in women: behavioral risk factor surveillance system, 2003. J Womens Health. 2006 Nov;15(9):1000-8.
6. Howard V.J. Reasons underlying racial differences in stroke incidence and mortality. Stroke. 2013 Jun;44(6 Suppl 1):S126-8.
7. Bernier M.O., Plu-Bureau G., Bossard N., Ayzac L., Thalabard J.C. Breastfeeding and risk of breast cancer: a meta-analysis of published studies. Hum Reprod Update. 2000 Jul-Aug;6(4):374-86.
8. Danforth K.N., Tworoger S.S., Hecht J.L., Rosner B.A., Colditz G.A., Hankinson S.E. Breastfeeding and risk of ovarian cancer in two prospective cohorts. Cancer Causes Control. 2007 Jun;18(5):517-23.
9. Jordan S.J., Cushing-Haugen K.L., Wicklund K.G., Doherty J.A., Rossing M.A. Breast-feeding and risk of epithelial ovarian cancer. Cancer Causes Control. 2012 Jun;23(6):919-27.
10. McClure C.K., Catov J.M., Ness R.B., Schwarz E.B. Lactation and maternal subclinical cardiovascular disease among premenopausal women. Am J Obstet Gynecol. 2012 Jul;207(1):46.e1-8.
11. Schwarz E.B., Ray R.M., Stuebe A.M., Allison M.A., Ness R.B., Freiberg M.S., Cauley J.A. Duration of lactation and risk factors for maternal cardiovascular disease. Obstet Gynecol. 2009 May;113(5):974-82.
12. Stuebe A.M., Schwarz E.B., Grewen K., Rich-Edwards J.W., Michels K.B., Foster E.M., Curhan G., Forman J. Duration of lactation and incidence of maternal hypertension: a longitudinal cohort study. Am J Epidemiol. 2011 Nov 15;174(10):1147-58.
13. Gunderson E.P., Jacobs D.R. Jr, Chiang V., Lewis C.E., Feng J., Quesenberry C.P., Sidney S. Duration of lactation and incidence of the metabolic syndrome in women of reproductive age according to gestational diabetes mellitus status: a 20-year prospective study in CARDIA (Coronary Artery Risk Development in Young Adults). Diabetes. 2010 Feb;59(2):495-504.
14. Stuebe A.M., Rich-Edwards J.W., Willett W.C., Manson J.E., Michels K.B. Duration of lactation and incidence of type 2 diabetes. JAMA. 2005 Nov 23;294(20):2601-10.
15. Schwarz E.B., Brown J.S., Creasman J.M., Stuebe A., McClure C.K., Van Den Eeden S.K., Thom D. Lactation and maternal risk of type 2 diabetes: a population-based study. Am J Med. 2010 Sep;123(9):863.e1-6.
16. Gunderson E.P., Hurston S.R., Ning X., Lo J.C., Crites Y., Walton D., Dewey K.G., Azevedo R.A., Young S., Fox G., Elmasian C.C., Salvador N., Lum M., Sternfeld B., Quesenberry C.P. Jr. Lactation and progression to type 2 diabetes mellitus after gestational diabetes mellitus: a prospective cohort study. Ann Intern Med. 2015 Dec 15;163(12):889-98.
17. Gunderson E.P., Hedderson M.M., Chiang V., Crites Y., Walton D., Azevedo R.A., Fox G., Elmasian C., Young S., Salvador N., Lum M., Quesenberry C.P., Lo J.C., Sternfeld B., Ferrara A., Selby J.V. Lactation intensity and postpartum maternal glucose tolerance and insulin resistance in women with recent GDM: the SWIFT cohort. Diabetes Care. 2012 Jan;35(1):50-6.
18. Chouinard-Castonguay S., Weisnagel S.J., Tchernof A., Robitaille J. Relationship between lactation duration and insulin and glucose response among women with prior gestational diabetes. Eur J Endocrinol. 2013 Mar 15;168(4):515-23.
19. O’Reilly M., Avalos G., Dennedy M.C., O’Sullivan E.P., Dunne F.P. Breast-feeding is associated with reduced postpartum maternal glucose intolerance after gestational diabetes. Ir Med J. 2012 May;105(5 Suppl):31-6.
20. Binns C., Lee M., Low W.Y. The long-term public health benefits of breastfeeding. Asia Pac J Public Health. 2016 Jan;28(1):7-14.
21. Kirkegaard H., Stovring H., Rasmussen K.M., Abrams B., Sorensen T.I., Nohr E.A. How do pregnancy-related weight changes and breastfeeding relate to maternal weight and BMI-adjusted waist circumference 7 y after delivery? Results from a path analysis. Am J Clin Nutr. 2014 Feb;99(2):312-9.
22. Martin J., MacDonald-Wicks L., Hure A., Smith R., Collins C.E. Reducing postpartum weight retention and improving breastfeeding outcomes in overweight women: a pilot randomised controlled trial. Nutrients. 2015 Feb 25;7(3):1464-79.
23. Schwarz E.B. Invited commentary: Breastfeeding and maternal cardiovascular health—weighing the evidence. Am J Epidemiol. 2015 Jun 15;181(12):940-3.
24. American Academy of Pediatrics Section on Breastfeeding. Breastfeeding and the use of human milk. Pediatrics. 2012 Mar;129(3):e827-41.
25. Saadeh M.R. A new global strategy for infant and young child feeding. Forum Nutr. 2003;56:236-8.
26. Centers for Disease Control and Prevention. Breastfeeding Report Card United States. 2018. Available at: http://www.cdc.gov/breastfeeding/data/reportcard.htm. Updated August 20, 2018. Accessed November 13, 2018.
27. Centers for Disease Control and Prevention. Rates of any and exclusive breastfeeding by socio-demographics among children born in 2012. Available at: http://www.cdc.gov/breastfeeding/data/nis_data/rates-any-exclusive-bf-socio-dem-2012.htm. Accessed November 13, 2018.
28. Jones K.M, Power M.L, Queenan J.T, Schulkin J. Racial and ethnic disparities in breastfeeding. Breastfeed Med. 2015 May;10(4):186-96.
29. McKinney C.O., Hahn-Holbrook J., Chase-Lansdale P.L., Ramey S.L., Krohn J., Reed-Vance M., Raju T.N., Shalowitz M.U. Racial and ethnic differences in breastfeeding. Pediatrics. 2016 Aug;138(2). pii: e20152388.
31. Jacobson L.T., Hade E.M., Collins T.C., Margolis K.L., Waring M.E., Van Horn L.V., Silver B., Sattari M., Bird C.E., Kimminau K., Wambach K., Stefanick M.L. Breastfeeding history and risk of stroke among parous postmenopausal women in the women’s health initiative. J Am Heart Assoc. 2018 Sep 4;7(17):e008739.
32. WHI Study Group. Design of the Women’s Health Initiative clinical trial and observational study. The Women’s Health Initiative Study Group. Control Clin Trials. 1998 Feb;19(1):61-109.
33. Hays J., Hunt J.R., Hubbell F.A., Anderson G.L., Limacher M., Allen C., Rossouw J.E. The Women’s Health Initiative recruitment methods and results. Ann Epidemiol. 2003 Oct;13(9 Suppl):S18-77.
34. Baird J., Jarman M., Lawrence W., Black C., Davies J., Tinati T., Begum R., Mortimore A., Robinson S., Margetts B., Cooper C., Barker M., Inskip H. The effect of a behaviour change intervention on the diets and physical activity levels of women attending Sure Start Children’s Centres: results from a complex public health intervention. BMJ Open. 2014 Jul 15;4(7):e005290.
35. Tong V., Dietz P., Morrow B., D’Angelo D.V., Farr S.L., Rockhill K.M., England L.J. Trends in smoking before, during, and after pregnancy—pregnancy risk assessment monitoring system, United States, 40 Sites, 2000–2010. MMWR Surveill Summ. 2013 Nov 8;62(6):1-19.