Infectious bugs may not just make you feel bad. Infections like herpes simplex and hepatitis A may also lead to cardiovascular disease and the deaths related to it.
That's the finding of a new study, conducted jointly by LDS Hospital, Johns Hopkins University and the Washington (D.C.) Hospital Center. They found a "strong" link between common infections and heart attacks, as well as cardiovascular deaths.Researchers from the three centers, including Dr. Joseph B. "Brent" Muhlestein, director of LDS Hospital's Cardiac Research Laboratory and an associate professor of medicine at the University of Utah, presented the results of the study, which involved 900 heart-disease patients, at the American College of Cardiology international meetings in Anaheim on Monday.
Muhlestein said researchers got interested "accidentally" in a link between chlamydia pneumoniae and development of atherosclerotic plaque in 1993. Then they started looking at other infections that could be related to heart disease and its outcomes. A year ago, LDS Hospital announced research indicating that the presence of cytomegalovirus in the blood of those with plague could significantly increase the risk of death.
"Our answer was to take a group of heart-disease patients and test them to see if a number of organisms, demonstrated by antibodies in the blood, predict a worse outcome.
"The results were more dramatic than anyone expected. Death from heart disease is nearly seven times more likely if all six bugs can be found." And the mortality rate "essentially rose in relation to the number of infectious agents that we tested for," Muhlestein said. "Patients with three bugs were three times more likely to die than those who didn't have an infection."
The six "bugs" were cytomegalovirus (CMV), hepatitis A, herpes simplex virus types 1 and 2, chlamydia pneumoniae and H. pylori.
The study focused entirely on patients who already had evidence of heart disease. A doctor affiliated with the National Institutes of Health had the same finding when he studied patients with and without heart disease.
What the study doesn't tell researchers is whether the infectious bugs stay "continuously active," or if the link to heart disease is an immune system response.
The study was controlled so that other risk factors, like age, sex and hypertension, would not influence the outcome of the study. In all, they eliminated 19 "confounding" variables, Muhlestein said. The presence of the virus' antibodies are "independently predictive."
The bugs are so common, in fact, that probably 65 percent to 75 percent of the population has been exposed to at least some of them, Muhlestein said.
Hepatitis A is less common and was almost left out of the NIH doctor's initial study because it seemed unlikely to have a role in heart disease. "It's a thing you get if you have bad food," Muhlestein said, "and you can recover completely. It's not like hepatitis B or C where there's a chronic active infection. So he put it in almost as a control. And he found it is strongly predictive, by itself."
The researchers believe now that a link has been established between infections and coronary disease, "maybe we can do things about it. We may be able to get better therapies."
Researchers are doing long-term antibiotic studies to see whether use of antibiotics is an effective treatment for patients with coronary artery disease. LDS Hospital is the only one in the Intermountain West taking part in that 25-hospital, $11 million study.