Infection with Chlamydia pneumoniae may increase the risk of heart attack in young men

Preliminary research suggests infection with Chlamydia pneumoniae may increase the risk of heart attack in young men, according to an article in the April 15 issue of Clinical Infectious Diseases.

C. pneumoniae is a relative of the more familiar bacterium that causes the sexually transmitted disease known commonly as chlamydia. The pneumoniae species, though, leads instead to respiratory problems such as pneumonia, bronchitis, and sinus infection and is not sexually transmitted. It is a common illness--by age 30, half of people have evidence of previous C. pneumoniae infection.

Researchers in Wisconsin and Maryland conducted a study of young men in the military to determine whether there was a link between C. pneumoniae infection and heart attack, also called myocardial infarction. They examined the blood of 600 men: 300 men between 30 and 50 years old who had been hospitalized for a previous heart attack, and 300 matched controls. Because the subjects were in the military, the researchers could examine blood samples that were collected and stored in the Department of Defense's serum repository before the men had their heart attacks. They found that high levels of C. pneumoniae antibodies in blood were associated with the occurrence of heart attack. This association was particularly strong in blood collected one to five years before the men's first heart attacks.

However, lead author Christine Arcari, PhD, of the University of Wisconsin cautions that the research is still preliminary, and much more data will be needed to confirm the link. "We don't understand how chlamydia fits into the pathogenesis of [heart attacks]," she said. "We don't fully understand why we're seeing this association on a biologic level." Past studies of C. pneumoniae's relation to heart attack have had conflicting results--some show an association between the bacterial infection and heart attacks, but others don't.

People with C. pneumoniae infections should not expect to prevent future heart attacks by getting antibiotic treatment for the bacteria, said Dr. Arcari. Again, the reasoning is based on experts' relative lack of knowledge about how C. pneumoniae relates to heart disease, as well as negative results in past trials. It isn't well understood how to eradicate the bacteria from the body, and once C. pneumoniae has set in, it may be too late to ward off heart attacks related to the infection. Further studies are being conducted to gather more information about the organism. Eventually, researchers may discover how to prevent C. pneumoniae infection altogether.