Those with blood type A are at a higher risk of early stroke, finds study

The study found that people with early stroke history were more likely to have blood type A and less likely to have blood type O (the most common blood type) — compared to people who suffer late strokes and people who have never had a stroke.

Both early and late strokes were also more likely to have blood type B compared to controls.

Early onset stroke was defined as an ischemic stroke occurring before age 60 and late onset stroke was older than 60.

Not clear why

“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,” said UMSOM Professor of Neurology Steven J Kittner in a statement.

The researchers emphasised 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 the study’s findings.

The meta-analysis included all available data from genetic studies focusing on ischemic strokes, which are caused by a blockage of blood flow to the brain, occurring in younger adults under age 60.

The meta-analysis involved a review of 48 studies on genetics and ischemic stroke from North America, Europe and Asia. The studies included 16,927 people with stroke and 576,353 people who did not have a stroke. Of those with stroke, 5,825 people had early onset stroke and 9,269 people had late onset stroke.

Rising number of early strokes

“The number of people with early strokes is rising. These people are more likely to die from the life-threatening event, and the survivors potentially face decades of disability. Despite this, there is little research on the causes of early strokes,” said Kittner.

“Non-O blood types have previously been linked to a risk of early stroke, but the findings of our meta-analysis showed a stronger link between these blood types with early stroke compared to late stroke, and in linking risk mostly to blood type A,” said study author Braxton D Mitchell of UMSOM in the statement.

The study has listed co-authors from over 50 institutions.