Someone in the U.S. has a stroke every 40 seconds, according to the Centers for Disease Control and Prevention (CDC). One of the scariest things about this kind of medical event—on top of the fact that it kills someone in the country every four minutes, the CDC points it—is that it can go completely undetected. A “silent” stroke injures the brain all the same but is not often realized until brain damage has progressed, according to the American Stroke Association.
But you may be able to tell if you’re more at risk of a stroke, whether silent or symptomatic, if you’re aware of the factors that contribute to this dangerous health condition—and it turns out, your blood type is one of those factors. Read on to find out which blood type is associated with an increased stroke risk, based on a new study, and for more things your blood type can tell you, check out If You Have This Blood Type, Your Heart Attack Risk Is Higher, Study Says.
At the American Stroke Association’s (ASA) 2021 International Stroke Conference, research funded by the National Institute of Neurological Disorders and Stroke looked at the association between blood type and stroke risk. According to the study, the researchers found that non-O blood types (A, B, or AB) may be at an increased risk of early-onset stroke for women who smoke and take oral contraceptives.
The researchers looked at nearly 350 women who had experienced a stroke before the age of 50 and compared their data to 383 women who had not had a stroke. They concluded that women with non-O blood types who smoked and took oral contraceptives were nearly twice as likely to have a stroke before turning 50.
“We sought to determine whether blood group, specifically non-O blood group, increases the risk for stroke among oral contraceptive users,” the study’s lead author Steven J. Kittner, MD, professor of neurology at the University of Maryland School of Medicine, said in a statement. “The results of our small study suggest that this might be the case, but more data from other studies are needed.” And for more on your health, If You Feel This at Night, You Need to Get Your Liver Checked, Doctors Say.
According to the study, no matter your blood type, women who both smoked and took oral contraceptives were nearly five times more like to have a stroke than women who did not smoke or take oral contraceptives. Breaking it down further, women who smoked, but did not take oral contraceptives had three times the risk of experiencing a stroke compared to non-smokers, while women who only took oral contraceptives but did not smoke were nearly four times more likely to have a stroke than those who did not take these pills.
“Due to this risk, women who smoke and are older than 35 should not take oral contraceptives,” the researchers said in a statement. And for more up-to-date health news sent right to your inbox, sign up for our daily newsletter.
This is not the only research to find a link between non-O blood types and strokes, however. According to a 2011 study presented at an American Heart Association conference, men and women with type AB blood had a 26 percent higher risk of stroke compared to those with type O blood, while women with type B blood had a 15 percent greater risk of stroke compared to women with type O blood.
JoAnn Manson, MD, one of the 2011 study leaders and chief of preventive medicine at Harvard’s Brigham and Women’s Hospital, said that one reason stroke risk may be higher among those with non-O blood types is because these blood types are more prone to blood clots, NBC reported. And blood clots are what lead to an ischemic stroke, which is the most common type of stroke, according to the Mayo Clinic. And for more on blood type, If You Have Type A Blood, You’re at Higher Risk for This Kind of Cancer.
As the CDC notes, stroke risk increases with age. The agency reports that the chance of having a stroke nearly doubles every 10 years after you reach the age of 55. That said, blood type, smoking, and oral contraceptive use are risk factors that contributed to women under the age of 50 experiencing early-onset stroke. The CDC says that experts also believe that “younger people are having more strokes because more young people are obese and have high blood pressure and diabetes.” And for more dangerous health concerns to be aware of, If You Can’t Do This in 90 Seconds, Your Heart Is in Danger, Study Says.