They found that individuals with a non-O blood group had a 9 percent greater risk of cardiovascular events, especially heart attacks, than those with an O blood type.

The researchers suggest one reason could be that people with non-O blood types have higher concentrations of von Willebrand factor, a blood-clotting protein that could lead to heart attack or stroke. Non-O blood groups are also known to have high cholesterol, especially those with blood type A