Your blood type just may help determine your risk for heart disease.

A new analysis suggests that having blood type O conveys some protection against heart attack and stroke, while having the far less common AB blood type appears to increase risk.

Heart disease risk typically takes into account measurable factors, such as a person’s blood pressure, cholesterol, and weight.

But blood type may also prove important, says researcher Lu Qi, MD, PhD, of Harvard Medical School and Harvard School of Public Health.

"People can’t change their blood type,” Qi says. “But we may be able to use this information to help determine a patient’s risk for heart disease and how aggressively to treat them.”

Slideshow: A Visual Guide to Heart Disease
Half of Americans Are Type O

Type O is the most common blood type in the United States.

About 45% of whites, 51% of African-Americans, 57% of Hispanics, and 40% of Asians in the U.S. have the blood type, according to the American Red Cross.

The AB blood type is much rarer. Only 4% of whites and African-Americans, 2% of Hispanics, and 7% of Asians in the U.S. have it.

In their new analysis, Qi and colleagues combined findings from two large studies that followed nearly 90,000 adults for at least two decades.

Compared to people with type O blood:

    People with the AB blood type were 23% more likely to develop heart disease.
    People with blood type A had a 5% increased risk.
    People with blood type B had an 11% increased risk.

Earlier studies suggest that the A blood type is linked to higher levels of LDL ("bad") cholesterol, and that the AB blood type is tied to inflammation, which is also linked to heart disease.

The findings appear in Arteriosclerosis, Thrombosis and Vascular Biology.
Does Blood Type Impact Treatment?

It's not yet clear if people with different blood types respond differently to preventive treatments such as cholesterol-lowering statin drugs, blood pressure medications, and even lifestyle interventions such as diet and exercise.

The study's findings need to be confirmed, says preventive cardiologist Richard A. Stein, MD, director of the exercise and nutrition program at NYU’s Center for the Prevention of Cardiovascular Disease.

“I actually don’t know the blood types of any of my patients, and I would imagine that most cardiologists will tell you the same thing,” he says. “Maybe this will prove to be useful in our assessments of how aggressively to treat patients, but we aren’t there yet.”