By DR. KITTU JINDAL GARG, ABC News Medical Unit
Does your blood type - A, B, AB or O - have implications for your health? A new study has raised the question of whether there is a link between blood type and heart disease.
A team led by Dr. Meian He, an epidemiologist in the Department of Nutrition at the Harvard School of Public Health in Boston, reviewed data from two large studies that looked at more than 85,000 people between 1976 and 2006. These participants were asked to report their blood type, as well as whether they had suffered a heart attack.
Analysis of the results found that individuals with non-O blood groups - meaning A, B, or AB - had a significantly higher likelihood of developing coronary heart disease.
The study was published Tuesday in the American Heart Association journal Arteriosclerosis, Thrombosis and Vascular Biology.
Blood type O is the country's most common, accounting for about 45 percent of Americans, according to the American Red Cross. Blood type A is second in line, and B is third. Blood type AB is the least common.
The research is the latest to suggest a relationship between blood type and a risk of heart disease. But not all heart experts are convinced there is a link.
"There are no clinical implications" of this week's study, said Dr. Steve Nissen, chairman of cardiology at Cleveland Clinic Foundation.
Dr. Jeffrey Brinker, cardiologist from Johns Hopkins University, agreed. "This type of study does not provide a degree of rigor that we usually consider necessary to definitely prove the point."
Specifically, these physicians say this study implies a relationship rather than cause-and-effect, and therefore may not be meaningful to patients.
Brinker added that he worries this information "would tend to inappropriately depress most people and inappropriately reassure the others," especially since blood type is genetic and Americans with non-O blood will wonder if they should be doing anything to protect themselves.
Some other cardiologists, however, say the study is potentially beneficial.
"This study adds to the existing literature demonstrating a significant association between ABO blood group and cardiovascular adverse events," said Dr. Jeffrey Berger, a cardiologist at NYU medical center. "This study is not novel - but the study is large - and is able to reinforce this message."
And theories have been proposed to explain this link. Many suggest that having type A, B or AB blood may result in higher levels of certain clotting factors in the blood, or it may predispose you to higher cholesterol levels.
Nevertheless, cardiologists say that no matter what your blood type, their advice remains the same.
"Live a healthy lifestyle and modify other modifiable risk factors [by] working with your health care providers," said Dr. Robert Eckel, director of the lipid clinic at University of Colorado.
In other words, he said, patients should focus on the risk factors they can alter such as tobacco use, exercise, weight loss, and controlling their cholesterol levels.