New Evidence Of Link Between Common Infection And Stroke
A Columbia Professor has Gathered Additional Evidence Linking a Common Bacterial Infection with Stroke
New York, NY – July 7, 2000 - In a study published in the July issue of the journal Stroke, Dr. Mitchell S.V. Elkind found that people infected with Chlamydia pneumoniae were four-and-a-half times more likely to have suffered a first ischemic stroke than their counterparts who had not been exposed to the bacterium. The association was consistent in people of all ages and ethnic groups studied and in both men and women. C. pneumoniae infects the respiratory tract and has also been found in the blood vessel walls of people with heart disease. The infection is common, and often mild. "Almost everyone gets it over the course of their life, perhaps two or three times,” says Dr. Elkind, who is assistant professor of neurology at Columbia University College of Physicians & Surgeons and assistant attending physician at the Columbia Presbyterian Medical Center of NewYork Presbyterian Hospital. “It may feel just like a cold.” The bacterium does not cause the sexually transmitted infection chlamydia, but is related to the organism responsible for this disease. Dr. Elkind and his colleagues investigated 89 stroke cases selected from the Northern Manhattan Stroke Study and 89 matched controls. They checked for C. pneumoniae infection with blood tests for antibodies to the bacterium. They used three tests: one for immunoglobulin A antibodies, which last in the blood for several days after C. pneumoniae exposure; immunoglobulin G antibodies to the bacterium, which stay in the body for several years; and immunoglobulin M antibodies. Antibodies are molecules the body's immune system makes in response to infection. The researchers used microimmunofluorescence to measure the levels of these antibodies. The team found that the shorter-lived IgA antibodies were strongly associated with the risk of having a first stroke. Having the IgG antibodies also increased stroke risk, but less severely than the IgA antibodies. A person with the IgG antibodies in his or her blood was about two and a half times as likely to have a stroke. None of the patients had elevated levels of IgM antibodies. If C. pneumoniae does increase stroke risk, the association is probably due to inflammation resulting from the infection, according to Dr. Elkind. He points out that researchers have been investigating the role of inflammation in heart disease and stroke since the 1950s. "Atherosclerosis looks like an inflammatory disease," says Dr. Elkind. "Evidence has been accumulating over the years that this is the case." An association between C. pneumoniae and heart disease was first observed by Scandinavian researchers in the late 1980s, he notes, adding, "The general idea is that infection with C. pneumoniae may be another thing, just like cholesterol and homocysteine, that is associated with atherosclerosis." Trials are now underway to investigate whether treating people with antibiotics reduces their risk of heart attacks. Dr. Elkind and his colleagues are also conducting a larger study of C. pneumonia and stroke. The research was supported by the National Institute of Neurological Disorders and Stroke, the General Clinical Research Center, the American Heart Association, and the Centers for Disease Control.