Understanding the Link Between Blood Type and Early Stroke Risk

A recent study suggests your blood type might influence your risk of an early stroke.

Every year, about 15 million people around the world suffer a stroke, says the World Health Organisation (WHO). Sadly, 5 million of these people die, and another 5 million are left permanently disabled. Stroke can be deadly, and its effects can be devastating. But what if we could predict who is at risk, especially for those under 60? It turns out, the answer might be in our blood.

A new study led by researchers at the University of Maryland School of Medicine (UMSOM) suggests that your blood type could hint at your risk of having a stroke before age 60. This could open doors to new ways to predict and prevent strokes in young adults. The findings are published in the journal Neurology.

What is a Stroke?

A stroke happens when blood flow to the brain is blocked or when there is sudden bleeding in the brain. There are two main types of strokes:

• Ischemic stroke: This occurs when the blood flow to the brain is blocked.
• Hemorrhagic stroke: This happens when a blood vessel in the brain ruptures and bleeds.

Ischemic strokes are the most common, making up about 87% of all strokes.

Blood Type and Stroke Risk

The new study found that a person’s blood type might be linked to their risk of having an early stroke. The researchers looked at data from genetic studies focusing on ischemic strokes in younger adults under age 60.

“The number of people with early strokes is rising. These people are more likely to die from a life-threatening event, and survivors potentially face decades with disability. Despite this, there is little research on the causes of early strokes,” said study co-leader Steven J. Kittner, MD, MPH, Professor of Neurology at UMSOM.

Kittner and his team analyzed 48 studies on genetics and ischemic stroke. They looked at data from 17,000 stroke patients and nearly 600,000 healthy people who had never had a stroke. The researchers found genetic factors linked to early strokes and identified variations that could explain higher risks in some people.

They discovered that people with early stroke were more likely to have blood type A and less likely to have blood type O (the most common blood type), compared to people with late stroke and those who never had a stroke. Both early and late stroke were also more likely to have blood type B compared to healthy people. The study found that people with blood type A had a 16% higher risk of having an early stroke, compared to other blood types. Those with blood type O had a 12% lower risk of having a stroke than people with other blood types.

What Do the Experts Say?

“Our study looked at people’s genetic profiles and found links between blood type and risk of early-onset stroke. The link between blood type and later-onset stroke was much weaker than what we found with early stroke,” said study co-leader Braxton D. Mitchell, PhD, MPH, Professor of Medicine at UMSOM.

They also pointed out that the increased risk was very small. People with type A blood should not worry about having an early-onset stroke or seek extra screening based on this study.

“We still don’t know why blood type A would carry 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 proteins in the blood, all of which play a role in the development of blood clots. We need more studies to understand the reasons for increased stroke risk,” said Dr. Kittner.

Previous studies have also suggested that people with blood type A have a slightly higher risk of developing blood clots in the legs, known as deep vein thrombosis.

“This study raises an important question that needs more investigation: how does our blood type, which is genetically determined, play a role in early stroke risk? It highlights the urgent need to find new ways to prevent these potentially devastating events in younger adults,” the researchers added.