People with blood type A may have a slightly higher risk of ischemic stroke before the age of 60, while people with blood type O may have a lower risk. ScienceAlert writes about this, citing a study published in the scientific journal Neurology.
The study is based on a meta-analysis of 48 genetic studies from North America, Europe and Asia. The sample included 16,927 people who had suffered a stroke and 576,353 people without a stroke. The scientists compared the genetic characteristics of people with early stroke, that is, before the age of 60, with data from people whose stroke occurred at a later age, as well as with a control group.
After adjustment for sex and other factors, the researchers found that people with blood type A had a 16% higher risk of early stroke compared with people with other blood types. In people with blood type O, the risk, on the contrary, was 12% lower.
In addition, the study showed that people with blood type B had an approximately 11% higher risk of stroke compared with the control group without stroke. Unlike blood type A, where the association was especially noticeable specifically for early stroke, the increased risk for blood type B was observed regardless of age.
Blood type AB was also included in the analysis; however, in the published conclusions of the study it was not singled out as a main independent risk factor for early stroke. The authors placed the main emphasis on the higher probability of early stroke among people with blood type A, the lower risk among people with blood type O, and the additional association of blood type B with the overall risk of stroke.
The authors emphasize that these data should not cause panic. The increase in risk is moderate, and blood type itself does not mean that a person will necessarily have a stroke. The researchers believe that the association may be due to blood-clotting mechanisms — the functioning of platelets, the condition of the vascular wall, and circulating proteins that influence the formation of blood clots.
An important conclusion of the work is that the association between blood type and stroke turned out to be stronger specifically for early strokes than for strokes at an older age. This may help scientists better understand why strokes among young adults are becoming more common and which additional biological factors may play a role besides blood pressure, smoking, diabetes, cholesterol, obesity and lifestyle.
For the healthcare system, such studies are important not as a reason to introduce mass screening by blood type, but as a step toward more precise prevention. If further studies confirm the mechanism of the association, doctors will be able to better identify risk groups among young patients and more carefully assess the combination of hereditary factors with the usual risk factors.
