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there are three stories in this series:

Do Healthier Gums Mean a Healthier Heart?

by angela spivey

They don't smoke. They keep their blood pressure and cholesterol low. But still, a heart attack strikes.

Why? Many researchers believe that inflammation — the body's response to a variety of assaults — may be partly responsible. "I think a large portion of the cardiovascular community might agree that inflammation is a risk factor for cardiovascular disease," says James Beck, professor of dental ecology. In fact, a researcher at Harvard Medical School, Paul Ridker, has shown that C-reactive protein, which is produced in the body as a response to inflammation, is a good predictor of heart attack.

Beck and Steven Offenbacher, professor of periodontology, think that one source of chronic inflammation could be infection in the mouth. Recently, Offenbacher, Beck, and Gary Slade showed that levels of C-reactive protein are a third higher in people with severe periodontal disease compared to people with little to no periodontal disease, even after controlling for other factors such as age, sex, and cigarette smoking. That study was published in the May 26, 2003, Archives of Internal Medicine.

Other facts support the idea that gum infections could contribute to heart disease. For one, periodontal disease is common — it affects about one in five people. It's a chronic, low-grade infection that can fester for long periods — so it has plenty of time to go to work on the heart. And, studies have shown a higher rate of periodontal disease among people who have heart attacks.

But because heart disease is so complicated, with so many risk factors, those findings are still controversial. Beck says, "There have been probably an equal number of studies that show heart disease is associated with periodontal disease as those that show it is not."

Others believe that any association between gum and heart diseases is just coincidental. For instance, some researchers point out that periodontal disease is also associated with cigarette smoking. Maybe much of the association between periodontal disease and heart disease is caused by cofactors such as smoking.

So Beck and Offenbacher are studying the potential link. Since 1994, the two have been working with Gerardo Heiss, professor of epidemiology in the School of Public Health and a lead investigator in the Atherosclerosis Risk in Communities (ARIC) study. The ARIC study follows thousands of people in four communities (in Mississippi, Maryland, Minnesota, and North Carolina) to find out more about heart-disease risk. Nine years into the study, the researchers added a dental exam to the medical evaluations that each subject receives.

In 2001, Beck, Offenbacher, Heiss, and colleagues published a study based on ARIC data that shows for the first time that periodontal disease is associated with an early sign of heart disease. Using data from more than 6,000 people, the team found that the chance of having a thickened carotid artery wall was higher in people with severe or moderate periodontal disease compared to those with no periodontal disease.

How might a mouth infection result in thickened arteries or other precursors of heart disease? A clue came in the early 1990s, when studies found DNA and RNA of certain bacteria in the plaques (lipid-filled deposits) that thicken arteries. One study of people with severe periodontal disease found oral bacteria in 42 percent of the subjects' arterial plaques. Some scientists suggest that oral bacteria and their associated toxins are released into the bloodstream, where they promote inflammation in the blood-vessel linings. This inflammation could play a role in formation of thickened arteries.

Others propose that bacteria themselves move through the bloodstream and end up in the arterial walls, where they set off reactions that cause plaque to grow. But for now, those are just theories. Figuring out if any of them hold won't be easy. Inflammation, for example, is a complex process that we don't understand well. "I'm not sure that we've identified the best way of characterizing the inflammation pathways and the response mechanism the body has to this sustained, low-level infection," Heiss says. Scientists have identified good markers of inflammation — we know when it is occurring. "But those markers aren't specific," Heiss says. "They don't tell us where the inflammation is coming from or which of many possible pathways is causing it."

Even if scientists never figure out the exact mechanisms, more work could still yield new treatments. If clinical trials show that finding and treating periodontal disease reduces heart attacks, "that will be another option that we can give people for improving their health," Heiss says.

Beck and Offenbacher are involved in one such trial, a pilot study in which researchers are recruiting people with known risk factors for heart disease. They will randomly treat half of the subjects for periodontal disease and leave the other half as a comparison group. If the patients who receive dental treatment show a decreased recurrence of heart attacks or other cardiac trouble, that could mean that a relatively simple intervention — forty-five minutes in a dental chair — could improve heart health.

Beck and Offenbacher emphasize that the link between periodontal disease and heart disease is still uncertain, and, if it does exist, the mechanisms are likely to be complicated. "Cardiovascular disease is really more than one disease," Beck says. "There's stroke, there's peripheral arterial disease, there's congestive heart failure." And Heiss adds that no one is saying that infection or inflammation is the sole cause of heart disease. He says, "It's just one more element to fill out the picture." end of story

Gary Slade, formerly of Carolina, is now professor of oral epidemiology at the University of Adelaide in Australia. The ARIC study is funded by the National Heart, Lung, and Blood Institute. The pilot study, led by Robert Genco of SUNY Buffalo, is funded by the National Institutes of Health.

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