Your blood type can tell you a lot about yourself, like your risk of certain health conditions, your risk of blood clots, and even if you’re prone to kidney stones. Now there is evidence that your blood type can also predict the risk of having a stroke.
Research recently published in the journal Neurology shows a strong association between blood group A and an increased risk of early ischemic stroke before the age of 60.
Stroke is one of the leading causes of death in the United States, according to the Centers for Disease Control and Prevention (CDC), whose data shows that a person has a stroke every 40 seconds and dies from it every 3 ,5 minutes. Nearly 90% of all strokes are ischemic strokes, which is when a blood clot prevents blood from reaching the brain.
While the new study suggests there is a strong genetic factor linking blood type to stroke, study co-author Braxton Mitchell, PhD, MPH, a genetic epidemiologist at the University School of Medicine of Maryland, said Health that you shouldn’t worry too much about your blood type.
“Overall, it’s a smaller risk factor than others,” Mitchell said, explaining that blood type is one of many genetic and environmental factors that increase a person’s risk of stroke.
Here’s an overview of how important (or weak) the role your blood type plays.
The researchers involved in the new study sought to understand the importance of genetics when it comes to a person’s risk of stroke. To do this, they conducted a genome-wide association study that included collecting data on stroke cases from around the world. The majority of the study data came from the United States and Europe.
From 48 different studies, the researchers analyzed the health information associated with nearly 17,000 stroke patients ranging in age from 18 to 59 years old. Over 599,237 medical cases not involving stroke served as controls. People were divided into four main blood groups depending on whether they had had an early stroke, a late stroke or no stroke.
The researchers searched for genetic variants across the genome and between study groups. They found significant genetic differences between patients who had had a stroke and those who had not. The differences were observed specifically in the genes encoding the ABO blood group.
“I was surprised that ABO blood type was by far the strongest association we’ve seen in early onset stroke,” says Dr. Mitchell. “And not only that, the association was much stronger for early strokes than for late strokes. So that was a surprise to us.”
Having type A blood was associated with an 18% higher risk of developing an early stroke. This included an increased risk of developing blood clots, which can trigger a stroke. In contrast, people with blood type O were 12% less likely to have an early stroke than other blood types.
There was also a slight risk of early and late stroke in people with type B blood. However, after the researchers adjusted for gender and other factors contributing to stroke, the association disappeared.
Sandra Narayanan, MD, a vascular neurologist and neurointerventional surgeon at the Pacific Neuroscience Institute, who was not involved in the study, said Health that the research adds to what scientists already know about uncontrollable risk factors for heart disease, such as the genetics that contribute to a person’s blood type.
However, Narayanan added that the findings could be the catalyst that people with a higher risk genetic profile for stroke need to make healthier lifestyle changes.
From a medical perspective, Dr. Narayanan added that understanding the genetic basis of stroke could “start the conversation about drugs or other strategies to reduce arterial or venous thrombosis.”
Because only 35% of participants were non-European, she adds that future studies with more diverse populations could help better understand the risks of stroke in blood types of different races and ethnicities.
Besides genetics and blood type, age is another factor that can increase your risk of stroke. The CDC warns that after age 55, your risk of stroke doubles every ten years. While strokes occur most often in people aged 65 and over, one in seven strokes occurs in people aged 15 to 49.
A person’s gender can also influence stroke. A 2022 review reports that women more than men are more likely to have stroke and a disproportionate burden of disability and death afterwards.
A separate study from 2022 calculated that young women aged 35 to 45 had a 44% higher risk of ischemic stroke than men of the same age. The CDC explains that women tend to be at higher risk of having a stroke due to pregnancy and the use of birth control pills.
Of all races and ethnicities, black people have the highest risk of stroke. The American Heart Association says one of the reasons black Americans have a higher prevalence of stroke is that two-thirds of this racial group tend to have at least one risk factor for stroke, including:
- Diabetes
- sickle cell anemia
- High blood pressure
- High cholesterol
- Obesity or overweight
Additionally, a 2021 CDC study suggests that black Americans have the worst outcomes. Black men, especially, faced the greatest risk of death from stroke and the lowest 5-year survival rate.
However, Dr. Mitchell said there are much more influential components than the uncontrollable risk factors mentioned above. “It’s a pretty rare occurrence,” he adds. “I would tell people that if you were really worried about your risk of stroke, I would look at your other risk factors and try to get them under control.”
It may come as a surprise, but around 80% of strokes are preventable, Dr. Narayanan said. To prevent a stroke from happening in the first place or reduce the risk of it happening again, she recommends these strategies for maintaining a healthy lifestyle. These include:
- Stop smoking or don’t smoke at all.
- Keep a blood pressure monitor at home if you have high blood pressure and keep track of your measurements daily. Dr. Narayanan says to bring these numbers with you or the diary to your doctor’s appointments. “Target BP is <140/90 mm Hg (or <130/80 mm Hg for patients with diabetes mellitus)."
- Eat a Mediterranean-style diet rich in fruits, vegetables, whole grains, fish, and nuts.
- Exercise. Research suggests that exercising for at least 2.5 hours per week for 3 months after a stroke improves a person’s overall health and quality of life. Dr Narayanan says even moving around for 10 minutes a day makes a bigger difference than doing nothing.
- Know your cholesterol level. “If you have ever had a stroke or [transient ischemic attack]aim for low-density lipoproteins (LDL < 70 mg/dL)."
“Consistency is the key to sustaining healthy lifestyle interventions. Start early. [About] 10-15% of strokes occur in adults under the age of 50,” advises Dr. Narayanan.
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