Yet another 'certainty' bites the dust

MEDICAL MATTERS:Link between gum and heart disease unfounded

DO YOU sometimes wish the medical profession would just make up its mind? Like should women self-examine their breasts for lumps or not? Or do calcium supplements do more harm than good?

The latest “certainty” to bite the dust is a 100-year-old belief that gum disease causes heart disease and stroke. An expert review group of cardiologists, dentists and infectious disease specialists has concluded this is not now the case. In its journal Circulation, the American Heart Association has published a review of some 500 journal articles and studies which has failed to find a causative link between gum disease and blockages in arteries.

Dentist Peter Lockhart, a co-chairman of the statement- writing group and professor of oral medicine at the Carolinas Medical Center in North Carolina, said observational studies have noted associations between gum disease and cardiovascular disease.

“There’s a lot of confusion out there,” Lockhart said in a statement. “The message sent out by some in healthcare professions that heart attack and stroke are directly linked to gum disease, can distort the facts, alarm patients and perhaps shift the focus on prevention away from well-known risk factors for these diseases.”

Gum disease and cardiovascular disease both produce markers of inflammation such as raised C-reactive protein, and share certain risk factors such as cigarette smoking, age and diabetes. These common factors may help explain why diseases of the blood vessels and mouth occur in tandem. But this association does not amount to a cause-and-effect relationship, the review of the medical literature on cardiovascular and gum disease from 1950 to 2011 found.

Treating gum disease doesn’t prevent heart disease or stroke, the reviewers also concluded. While people with gum disease are about twice as likely to be affected by coronary artery disease as those without it, it seems the link may be because those who neglect their dental health may be less inclined to look after their hearts.

The original theory had a seductive simplicity to it: mouth bacteria enter the blood stream during dental procedures, and in some people when brushing teeth; inflammatory processes in the mouth were replicated in key arteries; these vessel walls were thickened as a result, setting the scene for plaque development in coronary and other arteries.

But dentists insist gum disease can contribute to other health conditions. According to Dr Robert MacGregor, president of the Canadian Dental Association, older people can aspirate bacteria from their mouth into their lungs, resulting in pneumonia.

“The other health risk we’ve long known in dentistry is association between periodontal [gum] disease and diabetes.”

Meanwhile, looking to the future of the role of inflammation in heart disease, the Cleveland Clinic has established a profile of biomarkers that measure both oxidation and inflammation levels. The idea is to try to better define individuals at risk and also to determine where they are on a spectrum of risk for an acute coronary event.

They include measuring myeloperoxidase (MPO), an inflammatory enzyme derived from white blood cells. These cells release MPO when they respond to plaque and damage in the walls of arteries. As markers of white blood cell activity, MPO levels could help determine heart attack risk.

Another substance, F2-isoprostane, is a marker of oxidative stress. It may have a role as a lifestyle marker, indicating diet and exercise patterns that could lead to premature heart disease.

Then there is Lp-PLA2, a vascular specific inflammatory enzyme. When an artery wall is damaged because of smoking or high blood pressure, it joins with cholesterol to enter the damaged area; the biomarker can be used to measure the amount of vulnerable plaque in the coronary arteries.

If medicine was a static science, there would be fewer instances of accepted wisdom becoming myth. Then again, if that was the case, progress would be glacial, with little in the way of the kind of scientific breakthrough demonstrated by the Cleveland Clinic.

mhouston@irishtimes.com