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Rare Blood Types Carry Increased Risk for Heart Disease

  • Jessica Berman

Vials of different blood types are pictured in a hospital.

Vials of different blood types are pictured in a hospital.

Not all blood is alike.

There are four blood groups, based on the presence of particular antigens. The types are known as A, B, AB -- the rarest type -- and O -- the most common.

Researchers have discovered that people with rare blood types are more likely to develop coronary artery disease than those with the most common blood type.

Compared to people with type O blood, those with type AB had a 23 percent increased risk of heart disease. Individuals with type B blood were 11 percent more likely than type Os to have coronary artery disease. And type As had a five percent increased risk.

The study was conducted by investigators at the Harvard School of Public Health in Boston, who analyzed data from two large U.S. studies: the Nurses’ Health Study, which tracked the health of more than 62,000 nurses, and the Health Professional Follow-Up Study that involved more than 27,000 men. The participants in both studies were followed for 20 years or more, and the findings of the Harvard study are consistent for men and women.

Senior author Lu Qi, a professor of population studies at Harvard, says a genetic analysis could tell doctors whether the usual recommendations for reducing the risk of heart disease, such as improved diet and exercise, would be effective for individuals with rarer blood types.

“If we found risk factors would cause a different response in people with different blood types, we can provide specific recommendations for people with different blood types," Qi said.

Forty-three percent of Americans have type O blood, compared to 57 percent who have either A, B or AB.

Compared to other blood types, previous studies have found that people with type A blood tend to have higher levels of cholesterol, the waxy substance that clogs arteries, while type B blood is associated high blood pressure. Both conditions are risk factors for coronary artery disease.

People with the rarest blood type, AB, have been been shown to have higher levels of circulating endothelial cells, which can cause inflammation and the formation of arterial plaques that can lead to clogged heart arteries.

But Qi says that having one of the rarer blood types does not necessarily mean a person is prone to heart disease.

“Carrying the blood type AB or A or B doesn’t mean the person will develop chronic heart disease for sure," he said. "What we found just [means] they are at higher risk to develop chronic heart disease.”

Qi says that regardless of their blood type, people should maintain a healthful lifestyle to reduce their risk of coronary artery disease.

An article on blood type and heart disease is published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.

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