By Merritt McKinney

NEW YORK (Reuters Health) - Common, chronic bacterial infections, including lung and urinary tract infections, as well as gum disease, may increase the risk of atherosclerosis, a build-up of fatty plaques in the arteries that could lead to heart attack, study findings suggest.

During the 5-year study, people with chronic bacterial infections were nearly three times more likely to develop new plaques in carotid arteries, which are the large arteries in the neck that deliver blood to the brain.

A build-up of fat in the neck arteries can increase the risk of stroke, and is a sign that heart arteries may be clogged as well.

``Our study provides strong evidence that chronic infection is a risk factor (for) atherosclerotic vascular disease,'' the study's lead author, Dr. Stefan Kiechl, of the University of Innsbruck in Austria, told Reuters Health. ``These data may offer new clues (about) future disease prevention.''

But Kiechl cautioned that widespread use of antibiotics to fight chronic infections--and hopefully prevent atherosclerosis--is not justified. Such an approach must first be tested for safety and effectiveness in clinical trials, some of which are already under way, he said. In the meantime, he recommended taking steps to reduce the risk of developing chronic infections, including improving oral health, eating a healthy diet and not smoking.

Previous research has suggested a link between infections and heart attacks, but few studies have examined the relationship between infections and atherosclerosis, which can lead to heart attack and stroke, Kiechl and his colleagues note in a report in the February 27th issue of Circulation: Journal of the American Heart Association (news - web sites).

The current study included 826 white men and women aged 40 to 79 years who were followed from 1990 to 1995. Participants underwent ultrasound scanning of their carotid arteries at the beginning and end of the study.

Chronic infections were present in 268 of the participants. Infections were more common in heavy smokers and drinkers, older people and individuals of low socioeconomic status.

During the study, 41% of participants developed new plaques in their carotid arteries, the researchers report. People who had chronic infections were 2.78 times more likely to develop new plaques than people who did not have any infections.

But not all infections were linked to an increased risk of atherosclerosis. The study found that only bacterial infections, not infections caused by viruses like cytomegalovirus, the herpes zoster virus or hepatitis B or C, increased the risk of artery disease.

Kiechl and his colleagues suspect that infection-related inflammation may play a role in the increased risk. Patients with infections who had high levels of inflammation tended to have a greater risk of atherosclerosis, they report. Another possible explanation, according to the authors, is that bacterial infections may trigger the immune system to turn against itself. This so-called autoimmune response may damage vessels, making it easier for fatty deposits to accumulate, they note.

SOURCE: Circulation 2001;103:1064-1070.