People with blood type O are significantly less likely to develop heart disease compared to those with any other blood type, scientists claim.

The latest findings reveal that people with blood type AB, the rarest of all blood types that is found in about 7 percent of the U.S. population, had the highest increased heart disease risk and are 23 percent more likely to have a heart condition compared to those with blood type O.

Those with type B had an 11 percent increased risk and those with type A had a 5 percent increased risk for heart disease compared to those with type O blood, the most common of all blood types with about 42 percent of Americans having type O blood.

"While people cannot change their blood type, our findings may help physicians better understand who is at risk for developing heart disease," study author Dr. Lu Qi, an assistant professor in the Department of Nutrition at the Harvard School of Public Health in Boston, said in a statement.

Knowing your blood type can help you stay healthy and avoid heart disease, researchers said.

It's good to know your blood type the same way you should know your cholesterol or blood pressure numbers," he said. "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."

The latest findings are based on participant data from two large well-known U.S. studies including 62,073 women from the Nurses' Health Study and 27,428 adults from the Health Professionals Follow-up Study.

All participants were between the ages of 30 and 75 and they were all followed for 20 years or more.

Harvard researchers had also accounted for participants' diet, age, body mass index, gender, race, smoking status, menopause status, medical history and noted that the percentages of different blood types seen among the men and women participating in the two studies was similar to percentages seen in the general population.

Researchers did not assess the biological processes behind blood type and heart disease risk.

"Blood type is very complicated, so there could be multiple mechanisms at play," Qi said.

However, they said that there is scientific evidence to show that type A is associated with higher levels of low-density lipoprotein cholesterol or "bad cholesterol", the waxy substance that clogs arteries, and type AB is linked to inflammation, which may affect the function of the blood vessels.

Researchers added that a substance that plays a beneficial role in blood flow and clotting may also be higher in people with type O blood.

Qi recommended that better understanding of blood type could help healthcare providers better tailor treatments based on blood type. For example, patients with type A blood may best lower heart disease risk by decreasing cholesterol intake.

"It would be interesting to study whether people with different blood types respond differently to lifestyle intervention, such as diet," Qi said, noting that additional research is needed.

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

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