Is there a link between your blood type and risk of stroke?



Article By: Jessica Norris
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A stroke is a medical emergency that can lead to lifelong disability, and the risk of stroke can increase based on certain factors. A recent study found that people with type A blood may be at a higher risk for early onset stroke. Some factors, like blood type, cannot be changed but people can work to modify other stroke risk factors to reduce their chances of having a stroke.



Strokes are medical emergencies that cause damage to brain tissue. One of the most common types of stroke is an ischemic stroke where the blood supply to the brain is cut off.

A recent study published in Neurology found that people with type A blood had a higher risk of having strokes before age 60 when compared to people with type O blood.

However, people can work to reduce stroke risk by controlling modifiable risk factors like high blood pressure and heart disease.

How serious are strokes?
A stroke is a specific event that damages the brain or causes the death of brain tissue. The most common type of stroke is ischemic stroke. Ischemic strokes happen when something, such as a blood clot, blocks the blood supply to the brain. Without an adequate blood supply, the brain can’t get the oxygen it needs, and brain cells die because of the lack of oxygen.

The brain controls the rest of the body, so damage to it can cause long-term consequences. For example, people can experience memory loss, blindness, or communication problems after a stroke. They may also have paralysis on the side of the body opposite the side of the brain affected by the stroke.

Identifying risk factors for stroke can help increase awareness and hopefully prevent strokes.

The blood types that influence stroke risk
Certain factors increase stroke risk. However, there are some risk factors that experts have likely not identified and risk factors that are not totally understood. One area of interest is how blood type may increase stroke risk.

In this study, experts looked at blood type and its associated risk of early onset ischemic stroke (EOS). Early onset strokes are strokes that happen in people before age sixty.

Researchers performed a meta-analysis of genome-wide association studies. The data included research from 48 studies, ultimately analyzing data from 16,730 cases of stroke and 599,237 non-stroke control participants.

Including everything in the analysis, the greatest association for stroke risk had to do with blood types A and O.

The study found that people with type A blood were at the highest risk for early onset stroke. People who had strokes were also more likely to have type B blood compared to the control group. In contrast, people with type O blood had a decreased stroke risk, including early onset stroke.

This risk for stroke could be related to an increased risk for blood clots to form among people with type A blood.

Dr. Braxton D. Mitchell, study author and professor at the Departments of Medicine and Epidemiology and Public Health from the University of Maryland, noted the following highlights of the study to Medical News Today:

“We compared genetic differences between 16,730 young adults with ischemic stroke and ~600,000 non-stroke controls and found significant differences between the two groups in the frequency of gene variants that code for the ABO blood group. Specifically, cases were more likely than controls to have variants that coded for blood group A and less likely to have variants that code for blood group O[…]”

Dr. Mitchell further explained that “results indicate that blood groups may tag a heightened susceptibility to early onset stroke, perhaps by increasing susceptibility to thrombosis.”

“[W]e found that blood groups A and O were also more strongly associated with early onset compared to late-onset venous thromboembolism (VTE), another pro-thrombotic condition. Conversely, genetic risk of VTE was also more strongly associated with early onset compared to late-onset stroke.”
— Dr. Braxton D. Mitchell

Study limitations
This study was limited in a few ways. First of all, the study mainly included participants of European descent. This implies that more diverse follow-up is needed.

The study could also not determine the cause of this link between blood groups and stroke, so further data collection can focus on causal factors rather than association.

Finally, the sample size was still limited, limiting the researchers’ ability to look at unique subtypes and more detailed factors. Regardless, the study is a warning that many people can experience a stroke, and this knowledge should lead to addressing modifiable risk factors for stroke.

How to reduce your stroke risk
While people cannot change their blood type, there are other stroke risk factors that people can control to help reduce their risk. For example, high blood pressure, diabetes mellitus, high cholesterol levels, smoking, and obesity are all risk factors for stroke.

People can take steps to modify these risk factors and thus reduce stroke risk even if they have a blood type that may be more susceptible to stroke.

For example, people can follow healthy dietary recommendations and exercise regularly to help reduce stroke risk. People can be in close contact with their doctors and other medical professionals to push themselves toward a healthy lifestyle and address potential health problems.

Dr. Adi Iyer, a neurosurgeon of Pacific Neuroscience Institute at Providence Saint John’s Health Centre in Santa Monica, CA, who was not involved in the study, explained to MNT:

“If someone has an irregular heartbeat, it’s critical to see a physician immediately, as certain heart conditions can increase the chance of having a stroke.”

“Damage from a stroke can include weakness, numbness, speech difficulties, and even blindness. ..The best way to prevent a stroke is to not smoke cigarettes, exercise regularly, and eat healthy.”
— Dr. Adi Iyer

Lifestyle changes
Dr. Sandra Narayanan, board certified vascular neurologist and neuro-interventional surgeon at Pacific Stroke & Neurovascular Centre at Pacific Neuroscience Institute in Santa Monica, CA, who was not involved in the study, said that the findings served as a reminder that “being identified as having a riskier genetic profile for stroke may potentially serve as a positive impetus for lifestyle change, as well as initiate the conversation regarding medications or other strategies to reduce arterial or venous thrombosis.”

Dr. Narayan also shared with MNT some strategies to prevent first-time strokes and reduce the risk of them recurring, and said “up to 80% of strokes” could be prevented with the following lifestyle changes:

Quitting smoking
For those with high blood pressure, taking and writing down daily measurements via a blood pressure (BP) machine at home
Eating a Mediterranean-style diet rich in fruits, vegetables, whole grains, fish, and nuts
Doing regular exercise “in any form, even it’s just 10 minutes a day at first”
Knowing your cholesterol levels, and seeing the appropriate healthcare providers for routine follow-ups
Being consistent about maintaining such healthy lifestyle interventions
“This study adds to our body of knowledge on nonmodifiable risk factors for cerebrovascular disease. Healthy lifestyle interventions can accomplish much to prevent cerebrovascular disease from occurring or progressing. Start early. 10-15% of strokes occur in adults [younger than] 50 years of age.”
— Dr. Sandra Narayanan



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