A woman's risk of suffering a heart attack or stroke later in life may be influenced by how long she breastfed her children, according to a new study from China.
Women who reported having breastfed for any amount of time were about 9 percent less likely than mothers who never breastfed to have signs of coronary heart disease, like a heart attack, in middle age and later and about 8 percent less likely to have a stroke.
"This study suggests that it reduces the mother’s risk of developing cardiovascular disease," said study author Zhengming Chen, of the University of Oxford in the UK.
But, Chen told Reuters Health, the study does not prove a direct or causal link between not breastfeeding and poor cardiovascular health.
The American Academy of Pediatrics recommends that mothers exclusively breastfeed their children for the first six months of life, and continue to breastfeed for a year or more while introducing other foods.
Previous studies have linked breastfeeding to reduced risks of metabolic dysfunction, diabetes and high blood pressure among women later in life, Chen and colleagues note in the Journal of the American Heart Association.
Some studies have also suggested a link between breastfeeding and the risk of cardiovascular disease, they write.
For the new study, the researchers analyzed data on women who were recruited between 2004 and 2008, when they ranged in age from 30 to 79 years old, and were followed for about eight years. The analysis included 289,573 women living in 10 urban and rural areas of China, who provided information about their health and breastfeeding history. Researchers also gathered data about them from disease, death and insurance registries to see if they had heart-related events.
The women's average age was 51 when they entered the study. Nearly all reported giving birth to at least one child, and the vast majority breastfed at some point.
Over about eight years, the researchers found nearly 50,000 cases of cardiovascular disease, which included 23,983 strokes and 16,671 cases of coronary heart disease.
Women who had breastfed were 12 percent less likely to have cardiovascular disease, 9 percent less likely to have coronary heart disease and 8 percent less likely to have a stroke over that time than women who had children but never breastfed.
In addition, the risk of coronary heart disease and stroke appeared to decrease as the amount of time women breastfed increased.
Compared to women who never breastfed, those who reported breastfeeding for six to 12 months were 7 percent less likely to have a heart attack while the risk was 18 percent lower among women who breastfed for more than two years. The results were similar for stroke risk.
The researchers also adjusted the calculations to account for other factors that might influence the results like education, income, smoking status, blood pressure and physical activity.
"That didn’t really change our study findings at all," Chen said.
The new study can't explain the link between breastfeeding and heart health, but the researchers write that one possibility is breastfeeding helps women's bodies lose weight gained with pregnancy and "resets" their metabolism to improve the way their body uses insulin and processes fats in the blood, for example. These kinds of post-pregnancy changes may help set breastfeeding mothers on a path to better long-term health.
Still, women should not breastfeed to lower their cardiovascular risk, cautioned Dr. Steve Nissen, who is chair of the Robert and Suzanne Tomsich Department of Cardiovascular Medicine at the Cleveland Clinic in Ohio.
"Obviously people who breastfeed are different than people who don’t breastfeed," said Nissen, who wasn't involved with the new study.
"A 10 percent difference is so small that almost any unmeasured factor here could explain it," he told Reuters Health.
Nissen added that breastfeeding is favorable for infants. "We just don’t know if it’s favorable for the mother," he said.
