- People with blood type A are more likely to experience a stroke before age 60 than those with other blood types, according to one study.
- Researchers say more studies are needed to clarify the mechanisms behind this connection.
- Doctors share the simple lifestyle strategies that help lower your stroke risk, regardless of your blood type.
The majority of strokes occur in people over the age of 65, according to Stanford Medicine. But younger people can still have them—and research has uncovered a possible predictor. According to one study, certain blood types are at a higher risk of stroke before 60 than others.
Meet the experts: Braxton D. Mitchell, Ph.D., M.P.H., a professor of medicine at the University of Maryland School of Medicine; Steven J. Kittner, M.D., M.P.H., an adjunct professor of neurology at University of Maryland School of Medicine; Sandra Narayanan, M.D., a vascular neurologist and neuro-interventional surgeon at Pacific Stroke & Neurovascular Center at Pacific Neuroscience Institute in Santa Monica, CA.
In the study, which was published in the journal Neurology, researchers performed a meta-analysis of 48 studies on genetics and ischemic stroke that included 17,000 stroke patients and nearly 600,000 people who had never experienced a stroke. They then looked at all collected genetic data from the participants to identify genetic variations associated with a stroke and found a link between early-onset stroke (occurring before age 60) and the gene that determines whether a blood type is A, AB, B, or O.
The study found that people with early stroke were more likely to have blood type A (the second-most common blood type at 42% of people) and less likely to have blood type O (the most common blood type at 44% of people) compared to people with late stroke and people who never had a stroke. People with both early and late strokes were also more likely to have blood type B (held by 10% of people).
After researchers adjusted for sex, they found those who had blood type A had a 16% higher risk of having an early stroke than people with other blood types. Those who had blood type O had a 12% lower risk of having a stroke than people with other blood types.
“Our meta-analysis looked at people’s genetic profiles and found associations between blood type and risk of early-onset stroke. The association of blood type with later-onset stroke was much weaker than what we found with early stroke,” study co-principal investigator Braxton D. Mitchell, Ph.D., M.P.H., a professor of medicine at the University of Maryland School of Medicine, said in a press release.
According to the release from the University of Maryland, the team of researchers emphasized that the increased risk was very modest and that those with type A blood should not worry about having an early-onset stroke or engage in extra screening or medical testing based on this finding. But, it’s simply another reason to remain vigilant about your health.
“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,” study co-principal investigator Steven J. Kittner, M.D., M.P.H., an adjunct professor of neurology at University of Maryland School of Medicine explained in the release.
This study had its own set of limitations, most importantly a lack of diversity among participants. But since it was published in 2022, others have come out reinforcing the findings. One massive meta-analysis published in the Journal of Stroke and Cerebrovascular Diseases found that people with blood types A and AB are more likely to experience ischemic stroke, myocardial infarction (a.k.a. a heart attack), and peripheral vascular disease than people with blood type O.
Simple strategies to lower stroke risk
More than 50% of stroke survivors older than 65 have reduced mobility, which can lead to lower quality of life, said Sandra Narayanan, M.D., a vascular neurologist and neuro-interventional surgeon at Pacific Stroke & Neurovascular Center at Pacific Neuroscience Institute in Santa Monica, CA. “Stroke is the fifth leading cause of death and the leading cause of disability in the United States, but is the second leading cause of death in the world,” she adds. So even if you don’t have type A blood, it’s worth taking steps to lower your risk (especially if you do have other risk factors such as high cholesterol or diabetes).
Fortunately, there are many strategies that can help prevent a first-time cerebrovascular event or reduce the risk of recurrent stroke or TIA (transient ischemic attack or “mini-stroke”). According to Dr. Narayanan, up to 80% of strokes may be prevented with these lifestyle changes:
- Quit smoking.
- Keep a blood pressure (BP) machine at home if you have high blood pressure and take measurements daily. Write these down and bring the log to your doctor’s appointments. Goal 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—in any form, even if it’s just 10 minutes a day at first.
- Know your cholesterol. If you’ve already had a stroke or TIA, aim for low-density lipoprotein (LDL) of <70 mg/dL. Knowing your numbers and partnering with the appropriate healthcare providers (PCP, neurologist, cardiologist) for routine follow-up, medication adjustment, and lab work is critical.
- Consistency is key to maintaining healthy lifestyle interventions. Start early. 10–15% of strokes occur in adults <50 years of age.
The bottom line
This study adds to our knowledge of genetic and other unchangeable risk factors for diseases relating to the brain and blood vessels, said Dr. Narayanan. “As indicated above, healthy lifestyle interventions can accomplish much to prevent cerebrovascular disease from occurring or progressing. 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,” she added.
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