The study found that people with early stroke were more likely to have blood type A and less likely to have blood type O (the most common blood type) -- compared to people with late stroke and people who never had a stroke. Both early and late stroke were also more likely to have blood type B compared to controls. After adjusting for sex and other factors, researchers found those who had blood type A had a 16 percent higher risk of having an early stroke than people with other blood types. Those who had blood type O had a 12 percent lower risk of having a stroke than people with other blood types. “The association of blood type with later-onset stroke was much weaker than what we found with early stroke,” said Mitchell.
