Are You at Risk? How Your Blood Type Could Predict Early Stroke Risk

Your Blood Type and Stroke Risk: What You Need to Know

In a surprising new discovery, scientists have found that your blood type may affect your risk of experiencing an early stroke. Specifically, individuals with type A blood appear to be at a higher risk of having a stroke before the age of 60, compared to those with other blood types. While the study raises important questions about how blood type influences stroke risk, the findings are still part of an evolving area of research.

What Blood Type Has to Do with Stroke Risk

Blood types, those familiar labels like A, B, AB, and O, are more than just a medical classification. These blood types describe the various types of antigens found on the surface of red blood cells. While many of us associate blood type with simple transfusions, there’s growing evidence that blood type can also influence a wide variety of health outcomes, including the risk for stroke.

Blood types have been linked to various health conditions over the years, from heart disease to cancer. In this latest study, however, researchers focused on how blood type impacts the risk of stroke in younger populations—specifically those under 60. By looking at genetic data from nearly 600,000 participants, the research team uncovered some noteworthy correlations between blood type and the likelihood of early stroke.

The Study: What Researchers Found

The study, published in 2022, examined genetic data from 48 studies, involving more than 17,000 people who had suffered a stroke and almost 600,000 people without a stroke. Participants ranged in age from 18 to 59, providing a diverse group for assessing early onset stroke risks.

Using genome-wide data, the researchers discovered two specific regions in the genome that were strongly associated with an increased risk of an early stroke. Interestingly, one of these regions is where blood type genes are located. When the researchers examined different blood type variations, they found that individuals with a genetic variation of the A blood group had a 16% higher chance of experiencing a stroke before the age of 60, compared to individuals with other blood types.

A Lower Risk for Type O Blood

The findings weren’t all bad news. People with the O1 blood type, for example, had a 12% lower risk of having a stroke compared to others. This suggests that blood type, particularly type A, plays a role in determining stroke risk, though the increase in risk for those with type A blood remains small.

It's essential to note that while these findings may seem concerning, the overall risk increase for individuals with blood type A is still relatively low. As noted by Dr. Steven Kittner, the senior author of the study and a vascular neurologist at the University of Maryland, the study doesn’t mean people with type A blood should be alarmed. "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."

Blood Type A and Early Stroke: A Unique Connection

So why does blood type A appear to increase stroke risk? The researchers suggest that the increased risk might be due to the way blood type A impacts clotting factors. Blood clotting plays a crucial role in many strokes, particularly early onset strokes, which are less likely to be caused by the fatty plaque buildup that typically affects older individuals (a process called atherosclerosis). Instead, younger individuals are more likely to experience strokes due to clot formation, which could be influenced by their blood type.

In fact, the research found that the increased risk for people with type A blood disappeared when they looked at late-onset strokes, suggesting that strokes occurring later in life have a different mechanism than those occurring earlier.

Broader Context and Considerations

Although the study reveals an interesting link between blood type and early stroke risk, there’s still a lot we don’t know. For example, the participants in the study were primarily from North America, Europe, Japan, Pakistan, and Australia, with 35% of them from non-European backgrounds. Future studies with more diverse participants could help clarify whether the relationship between blood type and stroke risk applies universally across different ethnic groups.

Dr. Kittner also emphasized that more follow-up studies are necessary to uncover the underlying mechanisms behind these findings. Understanding these mechanisms could ultimately lead to better prevention and treatment strategies for those at higher risk for early stroke.

The Role of Blood Type B and Other Risk Factors

In addition to the findings related to blood type A, the study also explored the risk for individuals with blood type B. It was found that people with blood type B were 11% more likely to experience a stroke compared to individuals without a stroke, regardless of age. This aligns with previous studies suggesting that the ABO blood type gene may also be linked to coronary artery calcification, which is a known risk factor for heart disease and stroke.

Additionally, the study confirmed what previous research had suggested: the genetic sequence responsible for blood type is also associated with a slightly higher risk of developing blood clots, especially in veins (a condition called venous thrombosis).

Putting the Findings in Context

While the connection between blood type and stroke risk is intriguing, it's crucial to understand these findings in a broader context. Stroke remains a major health concern, with nearly 800,000 people experiencing a stroke each year in the United States. However, the vast majority of strokes occur in individuals over the age of 65, and the risk of stroke increases significantly with age.

The study adds another layer to our understanding of stroke risk, but it is unlikely to drastically change the way we approach stroke prevention in the general population. Still, for those with type A blood, being aware of the increased risk for early stroke could be an essential part of their overall health strategy.

Study Reference: https://www.neurology.org/doi/10.1212/WNL.0000000000201006