Research & Discovery

Q&A: Young People and Stroke – Your Blood Type May Increase Risk

By Eric Williamson, williamson@virginia.edu

September 13, 2022

Black lines connect blue and white abstract rectangles to an orange droplet

A certain blood type may increase the risk of early onset stroke in younger patients, while a different type apparently lowers the risk. (Illustration by Emily Faith Morgan, University Communications)

For the growing number of younger people who experience stroke, blood type matters, University of Virginia collaborative research has found.

The study, led by the University of Maryland, analyzed the genetic data of 16,730 patients ages 18-59 who suffered early onset stroke. Researchers were specifically interested in the area of the chromosome that determines A, AB, B, or O blood type.

Only types A and O showed significant associations. Having type A resulted in a 16% higher risk factor for stroke, while having type O demonstrated a 12% lower risk.

Why? For answers, UVA Today reached out to Dr. Bradford Worrall, vice chair for research in the Department of Neurology and one of the UVA Health researchers who contributed to the study, published Aug. 31 in the journal Neurology.

Worrall also addressed the surprising stroke trend and talked about what people can do to protect themselves.

Worrall, in a white coat, smiles at the camera

Q. Why are people having strokes earlier?

A. We are not entirely certain. Undoubtedly things like the obesity epidemic and its effects on the occurrence of diabetes, high blood pressure, and high cholesterol at younger ages is an important contributor. That said, we know that awareness of risk factors (and presumably treatment of them) has improved. Smoking has also decreased. So we need to investigate other factors that either influence the risk of stroke or alter the response to stroke risk factors like diabetes and hypertension.

Genetics offers us a way to learn about the biology underlying disease risk. Since atherosclerosis, or “hardening of the arteries,” is less common in younger folks, we sought to look at things that might influence the biological processes of clotting or thrombosis.

Q. Why did researchers think to look at the blood type connections?

A. The ABO locus – the part of the genome associated with blood type – has come up in earlier studies suggesting that alterations in this region of our DNA may influence the risk of forming blood clots and causing strokes.

Q. Why is type A worse to have? Why is type O better?

A. The exact biology remains to be sorted. We know that blood type affects clotting by influencing the levels of things like clotting Factor VIII and the Von Willebrand factor, both of which are important in the balance between forming and dissolving clots. People with type O have lower levels of both of these factors compared to those with other blood types. Blood type accounts for 20% of the variability of the levels of those factors in the blood.

Q. Do these blood type differences hold true for older people?

A. We did identify an association with genetic variation at the ABO locus in a study of ischemic (blockage) stroke in all adults. The difference is that the association with the specific blood types is stronger in younger individuals.

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Q. Do you have any special advice based on blood type?

A. No. The best advice is get screened for and address any stroke risk factors – high blood pressure, diabetes, high cholesterol and an irregular heartbeat called “atrial fibrillation.” And, if you smoke, stop. Smoking is the single most modifiable risk factor for stroke and heart attack. That risk can be truly eliminated. While the association with blood type offers us an important insight into mechanisms of stroke, especially at younger ages, the actual increase in risk for an individual is tiny, completely overwhelmed by known risk factors.

Q. How did UVA participate in the research?

A. We are part of a number of grants arising from the International Stroke Genetics Consortium including the Stroke Genetics Network, which is funded by the National Institute of Neurologic Disorders and Stroke. The Young Stroke project, led by our colleagues at the University of Maryland, arose out of those efforts.

Q. Anything else you wish to tell readers?

A. As Benjamin Franklin said, “An ounce of prevention is worth a pound of cure.” While we hope and expect that scientific advances like these will help us develop new treatments for ischemic stroke, the best approach is avoid having a stroke in the first place.