A stroke can happen to any person at any age—but thankfully, we know a bit more than that. We're aware, for example, about the well-known factors that can increase your risk of having one. These include health conditions such as high blood pressure, high cholesterol, heart disease, diabetes, and obesity, as well as behaviors like eating a high-fat diet, not getting enough exercise, and drinking too much alcohol. But now, researchers have found a new potential risk factor for stroke: your blood type.
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For a 2022 study published in the Neurology journal, researchers from the University of Maryland School of Medicine (UMSOM) performed a meta-analysis of data from 48 genetic studies that included roughly 17,000 people between the ages of 18 to 59 years old who had experienced an early-onset stroke, and nearly 600,000 healthy controls who had never had a stroke.
"Current genome-wide association studies of ischemic stroke have focused primarily on late-onset disease," the researchers explained. "As a complement to these studies, we sought to identify the contribution of common genetic variants to risk of early-onset ischemic stroke."
When comparing the two groups, they found a link between early-onset stroke—which is a stroke that occurs before the age of 60—and the area of the chromosome that includes the gene which determines your blood type.
"Our meta-analysis looked at people’s genetic profiles and found associations between blood type and risk of early-onset stroke," study co-principal investigator Braxton D. Mitchell, PhD, professor of medicine at UMSOM, said in a statement. "The association of blood type with later-onset stroke was much weaker than what we found with early stroke."
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According to the study, those who had experienced an early stroke were more likely to have blood type A. In fact, the researchers found that people with blood type A had a 16 percent higher risk of having an early stroke than people with other blood types.
"We still don’t know why blood type A would confer a higher risk, but it likely has something to do with blood-clotting factors like platelets and cells that line the blood vessels as well as other circulating proteins, all of which play a role in the development of blood clots,” study co-principal investigator Steven J. Kittner, MD, professor of neurology at UMSOM and a neurologist with the University of Maryland Medical Center, said in a statement.
On the other hand, those who had experienced an early stroke were less likely to have blood type O—which is the most common blood type. According to the study, people with blood type O have a 12 percent lower risk of having a stroke than people with other blood types.
"This study raises an important question that requires a deeper investigation into how our genetically predetermined blood type may play a role in early stroke risk,” Mark T. Gladwin, MD, executive vice president for Medical Affairs at UM Baltimore, added. "It points to the urgent need to find new ways to prevent these potentially devastating events in younger adults."
