Doctors have a new, and easy-to-determine way to predict a person's likelihood of heart trouble. Certain blood types carry a significant and inherent risk of CVD.

Researchers analyzed data from 62,073 women enrolled in the Nurses' Health Study (NHS) and 27,428 people enrolled in the Health Professionals Follow-up Study. Participants were between 30 and 75 years of age, and both groups were followed for at least 20 years.

Investigators found people with blood type A, B, or AB have a higher risk of developing CVD than those with blood type O. Luckily, blood type AB is the least common blood type in the U.S.: only about seven percent of Americans are type AB. Approximately 43 percent of Americans have type O blood. Study participants with blood type AB had a 23 percent increase in heart disease risk. Those with type B had an 11 percent increase in risk, and those with type A had a five percent increase in risk.

The findings may help physicians better understand who is at risk for developing CVD.

Study participants' diet, age, body mass index, gender, race, smoking status, menopause status, and medical history were also taken into account. The Harvard School of Public Health researchers say the distribution of different blood types seen among the men and women enrolled in the two studies accurately represented the distribution seen in the general U.S. population.

The findings may help physicians better understand who is at risk for developing CVD, said Lu Qi, the senior author of the study.

Qi, an assistant professor in the Department of Nutrition at the Harvard School of Public Health, went on to say that, "If you know you're at higher risk, you can reduce the risk by adopting a healthier lifestyle, such as eating right, exercising, and not smoking."

Although the study did not look at the biological processes behind blood type and CVD risk, scientific evidence suggests that type A is associated with higher levels of low-density lipoprotein (LDL) cholesterol, the so-called “bad cholesterol” that can clog arteries, and type AB is linked to inflammation, which may affect blood vessel function.

A more complete understanding of blood type may also help healthcare professionals better personalize treatment recommendations, Qi said. For example, persons with type A blood may best lower heart disease risk by decreasing cholesterol intake.

Qi said that future studies could focus on factors such as environment and ethnicity. "It would be interesting to study whether people with different blood types respond differently to a lifestyle intervention, such as diet," he said.

The study was published in the journal Arteriosclerosis, Thrombosis and Vascular Biology.