Your blood type may be linked to your risk of having an early stroke – before the age of 60 – according to a new study.
Researchers from the University of Maryland School of Medicine found that people with blood type A had a 16 per cent higher risk of having an early stroke than people with other blood types.
Those who had blood type O had a 12 per cent lower risk of having a stroke than people with other blood types.
These findings came from a rigorous meta-analysis “of all available data” from genetic studies of ischaemic strokes that had occurred in younger adults.
Ischaemic strokes are caused by a blockage of blood flow to the brain.
For people with type A blood this will be freaky news. But the researchers have emphasised that the increased risk is “very modest”.
On the one hand, they advise that people 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”.
On the other hand, eating more salmon, cutting out cigarettes and getting some regular exercise might help even out the odds.
How did they make their findings?
Co-principal investigator Steven J Kittner, professor of neurology at Maryland, said the number of people with early strokes is rising.
“These people are more likely to die from the life-threatening event, and survivors potentially face decades with disability,” he said.
“Despite this, there is little research on the causes of early strokes.”
The obesity epidemic no doubt plays a part. So does the notoriously poor Western diet and widespread failure to meet exercise guidelines.
But lifestyle factors aren’t the whole story. And the role of genetics is far from being wholly understood, beyond some rare inherited disorders.
The Maryland scientists basically took a punt, performing a meta-analysis of 48 studies on genetics and ischaemic stroke “that included 17,000 stroke patients and nearly 600,000 healthy controls who never had experienced a stroke”.
When they looked across all collected chromosomes to identify genetic variants associated with a stroke, they found a link between early-onset stroke “and the area of the chromosome that includes the gene that determines whether a blood type is A, AB, B, or O”.
There’s potential guilt by association here, rather than a direct link between blood type and stroke.
In terms of rating the apparent risk:
- Blood type A was associated with the highest risk of suffering early onset stroke
- Blood type B sat in the middle. Both early and late stroke were more likely to have blood type B compared to controls
- Type O, the most common blood type, was the least likely to be associated with early-onset stroke, which are suffered before the age of 60.
But why blood type?
Professor Kitner said: “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.”
He said that previous studies suggest that those with an A blood type have a slightly higher risk of developing blood clots in the legs (deep vein thrombosis).
“We clearly need more follow-up studies to clarify the mechanisms of increased stroke risk,” he said.
