There are two types of stroke. A hemorrhagic stroke occurs when an artery in the brain ruptures and the blood flow causes brain cells to die. Ischemic stroke is characterized by blockage of an artery. It may be blocked by a blood clot or a fatty deposit. The blocked area is no longer irrigated with blood. Without oxygen supply, the area may be irreversibly affected. To find out who may be most at risk for ischemic stroke before the age of 60, the University of Maryland conducted a large meta-analysis published in the journal. Their results show that there is indeed a difference in risk based on blood type.
“Most strokes occur at an older age. Because of this, we chose a cut-off age of 60 for our study, in part to include stroke cases that are relatively young compared to the age at which strokes typically develop,” explains Dr. Braxton Mitchell. specialist in epidemiology and public health at Sciences et Avenir. To do this, the team reviewed 48 written studies on the subject, including 17,000 stroke victims, as well as 600,000 control patients who had never had an ischemic stroke. All were between 18 and 59 years old.
A is more at risk than O
The results showed that there is indeed a difference in blood types. People with type A had a 16% higher risk of early stroke than people with other blood types. People with blood type B have an 11% increased risk of stroke. The likelihood of an early stroke in people with type O was 12% lower than in people with other blood types. In addition, the relationship between blood type and the occurrence of stroke was very noticeable for early strokes.
But this association was weaker for strokes that occur later in life. The researchers used a different sample of 9,300 people with stroke and 25,000 people without stroke, this time over the age of 60. It turned out that with age, the relationship between group A and increased risk ceases to be significant. Group B still posed a greater risk of 11%, as did patients under 60 years of age.
Why is group A at greater risk than group O before age 60? The team has not determined the cause at this time. “However, we believe that blood type predisposes people to blood clotting,” Dr. Mitchell explains to Sciences et Avenir. Excessive blood clotting leads to the appearance of blood clots, which are responsible for the occurrence of ischemic strokes. “We also found that blood type A is associated with early venous thromboembolism, another bleeding disorder.Another clue that may help researchers in future work.
Don’t worry if you belong to group A
The authors of the study are formal: people with blood type A should not worry too much. There is no need to undergo screening tests or special medical examinations. “It is important to emphasize that people with blood type A should not be particularly concerned about the risk of stroke. Blood type is a much weaker risk factor than other modifiable risk factors for stroke, such as high blood pressure and smoking. For people who want to reduce their risk of stroke, these are the main factors to consider.”
Regardless of their blood type, taking care of hypertension and not smoking are the two most important ways to manage stroke risk. Experts also do not exclude that blood type A enhances the effect of hypertension and smoking on strokes; they highlight the need for further research to better understand this phenomenon. Note that during the Covid-19 study, group O also appeared to be more protected, while group A posed more risks.