German Study Links Infection, Heart Disease
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Researchers in Germany said on Monday they had found more evidence that infections with bacteria that cause pneumonia, ear infections and other diseases may also cause heart disease.
The study, in the American Heart Association journal Circulation, adds to a growing body of evidence that the body's response to some infections may help cause heart disease.
"We showed a significant association between the number of infections to which a patient has been exposed and the extent of atherosclerosis in the arteries in the heart, neck and legs,'' Dr. Hans Rupprecht and Dr. Christine Espinola-Klein of Johannes Gutenberg University in Mainz, Germany, who conducted the study, said in a statement.
"The risk for death was increased by the number of infectious agents, especially in people with advanced artery disease.''
Researchers believe it is the body's inflammatory response to an infection that helps, along with a fatty diet, to clog arteries. The plaques that form these clogs are created when immune system cells latch onto fat cells in the blood and try to pull them out through the cell wall.
The fat cell is often too big and it gets caught. Thetrapped immune and fat cells build up in the artery wall, harden and can block blood flow or break off into clots.
Inflammatory responses to infection can send more of these immune cells circulating, looking for something to do.
Rupprecht's team tested 572 patients with heart disease, most of whom had chest pain or heart attack.
EIGHT MICROBES ASSOCIATED WITH HEART DEATH
They looked herpes simplex virus 1 and 2, which cause cold sores and genital herpes; cytomegalovirus, which is another herpes virus; Epstein-Barr virus, which causes mononucleosis; Hemophilus influenzae, a bacteria that causes ear and upper respiratory infections; Chlamydia pneumoniae, which can cause pneumonia; Mycoplasma pneumoniae, another cause of pneumonia; and Helicobacter pylori, which causes most stomach ulcers.
Over the next three years, Rupprecht's team wrote, they found a clear correlation between how many infections a person had and his or her risk of dying from heart disease.
"The antibody titers (levels) for C. pneumoniae, H. pylori, H. influenzae, cytomegalovirus, and herpes simplex virus type 2 were related to the extent of atherosclerosis,'' Espinola-Klein said in an interview conducted by e-mail.
In patients who tested positive for up to three infections, the death rate was 3.1 percent. The death rate was 9.8 percent for those infected with four to five agents and 15 percent for those with six to eight pathogens.
Twenty percent of the patients with advanced atherosclerosis who had six to eight infections died, compared to 7 percent of those with three exposures or fewer.
"Based on these results, we think that the number of infections to which an individual has been exposed may be involved in the development and progress of atherosclerosis. Both bacterial and viral pathogens seem to be involved,'' Espinola-Klein said.
But Dr. Paul Ridker, director of the Center for Cardiovascular Disease Prevention at Brigham and Women's Hospital in Boston, said the link may not necessarily mean that infections cause heart disease.
They could just be a marker for something else. For example, Ridker said in a commentary, people with a lot of infections could be in poorer health in general.
Ridker, who also studies links between infection and heart disease, has found that healthy people with high levels of inflammatory cells are more likely to develop heart disease.
"Our results suggested that inflammation seems to be a fundamental issue,'' he said, and noted that other studies indicate that aspirin and cholesterol-lowering statin drugs may prevent heart disease at least in part by reducing inflammation.
Last November, a Swedish team reported in the Journal of the American Medical Association that elevated levels of interleukin 6, one of the body's inflammatory signaling chemicals, could predict deaths from heart disease.
And last February an Austrian team reported that people who get infections over and over again, such as sinus infections or bronchitis, may also be more prone to clogged arteries.
But although several studies have linked infection with heart disease, none has shown that people who took antibiotics had a lower risk of heart disease.
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