Study Finds New Risk Factor for Stroke and Heart Attack
For immediate release: August 02, 2001
Researchers studying the risk factors for stroke and heart attack say they have identified an antibody that seems to double the risk of both health problems in men, independent of other risk factors. Their study, published in the August issue of the journal Stroke, is the first prospective study to show that the risk of ischemic stroke and heart attack is increased among men who have these particular antibodies, known as Beta-2 Dependent Anticardiolipin Antibodies (B2GP1-dependent aCL).
"Our study found that the risk of stroke and heart attack associated with these antibodies was similar to the increased risk from other conditions, such as hypertension and diabetes," says Steven J. Kittner, M.D., M.P.H., professor of neurology at the University of Maryland School of Medicine and a neurologist at the Baltimore VA Medical Center. Dr. Kittner is the study's senior author.
For the study, the researchers evaluated blood samples from men of Japanese ancestry who were followed over the past 20 years as part of the Honolulu Heart Program. They measured the antibodies in 259 men who went on to have an ischemic stroke (caused by a blockage in a blood vessel) and 374 men who developed a heart attack. They also studied blood from a control group of 1,360 men who remained free of both health problems.
Men with the antibodies had a two-fold increased risk of stroke, and for heart attack the risk was almost twice as high, when adjusted for other risk factors. While it is clear that uncontrolled hypertension, diabetes, high cholesterol, and smoking increase the risk of cardiovascular disease, the researchers say they do not know all of the predisposing risk factors. There are still many people who suffer from these common health problems who do not seem to be at high risk.
Our bodies form antibodies after they are exposed to infection, and the role of inflammation and infection in cardiovascular disease is a major focus of research now, as part of the effort to better prevent, predict and treat heart disease and stroke. But there are many unanswered questions.
"While we found a striking association between these particular antibodies and heart attack and stroke, we do not know whether they are a cause or merely a precursor for these events," says Dr. Kittner. "We need more research to determine if there is a cause and effect relationship. Or, it could be that something else, such as a particular infection, is causing both the antibodies and the stroke or heart attack," Dr. Kittner adds.
The researchers also want to learn whether people who have these antibodies should be treated differently after they have a heart attack or a stroke. Robin L. Brey, M.D., associate professor of medicine at the University of Texas Health Science Center at San Antonio, says this study will help answer those questions.
"Now that we have proof that these antibodies are markers for increased risk, we can turn our attention to how they are associated with stroke and heart attack. We now need to explore whether these antibodies cause stroke or heart attack, and try to better understand the mechanism, if they are found to be causative," adds Dr. Brey, who was the lead author of the study. "The next step will be to use information about mechanism to develop better strategies to decrease stroke and heart attack risk for people with these antibodies," she adds.
The B2GP1-dependent aCL antibodies were found in about 12 percent of men in the study who did not have cardiovascular disease, but they were prevalent in 17 percent of men who had a stroke and 16 percent of those who had a heart attack. Scientists do not know which type of infection, if there is one, may be responsible for these particular antibodies.
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