Study Links A1 Blood Type to 16% Higher Stroke Risk Before 60

3 articles · Updated · ScienceAlert · May 23

Researchers analyzing 48 genetic studies found the A1 blood subgroup was tied to a 16% higher risk of stroke before age 60, while the O1 subgroup was linked to a 12% lower risk.
About 17,000 stroke patients and nearly 600,000 controls aged 18 to 59 were included, and the strongest signal appeared at the ABO blood-type gene locus.
The association faded in later-life strokes: a separate analysis of about 9,300 stroke cases over 60 found type A's added risk was no longer significant, pointing to different mechanisms in younger patients.
Researchers said the absolute added risk is small and does not warrant extra screening, though clotting-related factors may help explain the link.
The findings, published in Neurology, add to evidence that blood-type genes affect clotting and cardiovascular risk, but the sample was only 35% non-European ancestry, leaving follow-up studies needed.

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