Researchers have found that people with blood type A may be more likely to have a stroke before the age of 60 compared to other blood types.
In contrast, those with blood type O are less likely to have an early stroke, according to a new meta-analysis.
The research was conducted by a team led by scientists from the University of Maryland School of Medicine in the United States, who looked at the relationship between genetic characteristics such as blood type and their relationship to stroke.
To do this, they looked at data from 48 genetic studies about ischemic strokes in adults ages 18 to 59. Ischemic strokes occur due to blockage of blood flow to the brain.
In total, the studies included about 17,000 patients with stroke and nearly 600,000 healthy people who did not have a stroke.
“We were interested in trying to identify the genetic determinants of stroke,” Braxton Mitchell, the study’s co-lead researcher, told Euronews.
“For stroke, we’ve known for a long time that there’s a big environmental component, but there’s also a genetic component,” said Mitchell, a professor of medicine at the University of Maryland School of Medicine.
To examine this further, he and his colleagues looked through people’s genetic profiles, and ended up finding a link between early stroke and a region of the chromosome that includes the gene that determines a person’s blood type.
Humans have four main blood types, A, B, AB, and O, and a person’s blood type is determined by the genes they inherit from their parents. Blood type O is the most common.
What the researchers found was that those who had an early stroke were more likely to have blood type A and less likely to have blood type O, compared to people who had late stroke and people who did not have a stroke.
“Having type A blood increases the risk of early stroke by about 16 percent, but only about 5 percent for later onset of stroke,” Mitchell said.
“If you have blood type O, you are 12 percent less likely to have an early stroke, compared to just 4 percent less likely to have a later stroke.”
Very modest increased risk of stroke
But although the researchers found associations between having blood type A and the risk of early stroke, they emphasized that the increased risk was very modest.
They stress that those with type A blood should not worry about having an early stroke, or engage in additional screening or medical testing based on this finding.
“Clinically speaking, we shouldn’t worry about the blood types that put us at risk for stroke,” Mitchell said.
“There are other risk factors for stroke that are more important, like high blood pressure and smoking, for example. So if we want to reduce the risk of stroke, these are the factors we really have to pay attention to.”
He added, “Having said that, what we’re wondering is if you have these risk factors, and you also have blood type A, does that make those risk factors more powerful? We don’t know that yet. But that’s one of the things we’re looking at.”
It is still not clear why blood type A increases this elevated risk, but researchers believe it may have something to do with blood clotting factors.
Other studies have suggested that people with blood type A have a slightly higher risk of developing blood clots in the legs – known as deep vein thrombosis.
“This kind of pro-thrombotic background of having type A blood is likely to put you at greater risk for clotting-related diseases, including stroke,” Mitchell said.
One limitation of the analysis was the relative lack of diversity among the participants, most of whom were of European descent, with the researchers welcoming further follow-up studies on a more diverse population.
“We all have different genetic variants, and often genetic variants tend to cluster within different breed groups,” Mitchell said.
“So maybe we’re missing some important variables by just looking at a small representation of the strain groups.”
Blood type linked to risk of other diseases
It’s not just about stroke risk – other research has suggested links between blood type and risk of other health conditions.
For example, a study by scientists from Harvard School of Public Health It was found that people with blood type A, B or AB have a higher risk of coronary heart disease than people with blood type O.
Those with the rarest blood type, AB, were most at risk.
Other studies have suggested that people with type A blood have a higher risk of infection stomach cancercompared with other blood groups.
It should be noted that although studies have shown an association between blood type and certain health conditions, we still do not know the reasons for these relationships.
So, if you have type A blood, how concerned should you be?
Mitchell points out that no person can truly change their blood type. There are other risk factors for stroke that are within a person’s control, such as nicotine habits, blood pressure, alcohol use, and amount of exercise.
“I would say, don’t worry at all,” Mitchell said. “I will think about other modifiable risk factors and focus on them, because they are not only risk factors for stroke, they are risk factors for heart disease, cancers and so on.”
A ‘big step’ towards helping reduce stroke risk
Commenting on the findings, Claire Jonas of the charity Stroke UK said the findings were a “big step” towards better monitoring of risk factors for early stroke.
“The majority of strokes occur in older adults, for reasons we are generally aware of such as high blood pressure, thickening of the arteries, or atrial fibrillation,” said Jonas, chief of research communications and engagement with the Stroke Association. Provides support for people who have had a stroke.
“The causes of stroke in younger adults are not well understood, making it more difficult to prevent,” she said in a statement.
“We don’t yet know why people with blood type A have an increased risk of early stroke. This means that we cannot yet develop targeted prevention of early stroke.”
“However, this research is a great step toward helping healthcare professionals see who would benefit most from monitoring for other risk factors and providing interventions to help reduce risk,” she added.