Your blood type is connected to your risk for an early stroke, study finds

A recent meta-analysis conducted by the University of Maryland School of Medicine (UMSOM) suggests there may be a connection between blood type and the risk of experiencing an early stroke. The study, published in Neurology, focuses on ischemic strokes, which occur due to blocked blood flow to the brain and often impact individuals under 60 years old.

According to Dr. Steven J. Kittner, a neurology professor at UMSOM and co-principal investigator, early strokes are becoming more common and significantly impact both life expectancy and quality of life. Yet, research on the causes of early strokes remains limited.

This meta-analysis reviewed data from 48 genetic studies involving over 17,000 stroke patients and nearly 600,000 healthy individuals. The goal was to find genetic variants linked to stroke risk. Notably, the researchers identified a link between early strokes and a specific chromosome region that influences blood type.

The findings showed that individuals with blood type A were more likely to experience an early stroke, while those with blood type O, the most common type, had a lower risk.

For people with blood type B, there was an increased risk of both early and late strokes compared to the general population. Specifically, those with blood type A had a 16% higher risk of early stroke, while those with blood type O had a 12% lower risk compared to others.

Dr. Braxton D. Mitchell, another co-principal investigator and professor of medicine at UMSOM, emphasized the significant association between blood type and early stroke risk that emerged from the analysis. However, he advised that the increased risk should be interpreted cautiously, describing it as modest. He did not recommend additional medical testing purely based on blood type.

Researchers believe that blood-clotting mechanisms might play a role in the link between blood type and stroke. Factors like platelets, endothelial cells, and circulating proteins—all of which are involved in clot formation—could underlie this connection.

Previous studies have indicated that individuals with blood type A may be at higher risk of deep vein thrombosis, a type of blood clot in the legs, which supports these findings.

Despite this insight, Dr. Kittner pointed out the need for further research to understand the biological mechanisms responsible for the elevated stroke risk in individuals with blood type A. He stressed that multiple biological factors are involved, and more work is required to explore these elements in depth.

One limitation of the study was the lack of diversity among participants. Approximately 35% of the individuals were of non-European ancestry. The data analyzed came from the Early Onset Stroke Consortium, which includes research from 48 different studies conducted across the world.

Dr. Mark T. Gladwin, a professor at UMSOM and Executive Vice President for Medical Affairs at the University of Maryland Baltimore, stressed the importance of this research in highlighting how genetic factors, like blood type, might contribute to early stroke risk. He also emphasized the need for prevention strategies to address the severe consequences of early strokes, especially in younger adults.

Alongside Dr. Kittner and Dr. Mitchell, numerous UMSOM faculty members contributed to the study, including Dr. Huichun Xu, Dr. Patrick F. McArdle, Dr. Timothy O'Connor, Dr. James A. Perry, Kathleen A. Ryan, Dr. John W. Cole, Dr. Marc C. Hochberg, Dr. O. Colin Stine, and Dr. Charles C. Hong.

The study also had support from the National Institutes of Health and the Department of Veterans Affairs, with co-authors from more than 50 institutions worldwide.

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