By SUSAN GILBERT
August 05, 2003
Your dental health may be a sign not only of how diligently you brush and floss but also of your risk of stroke and heart disease.
A number of studies have indicated a relationship between periodontal disease and a heightened risk of developing problems with the heart or circulatory system. But pinning down those suspicions has proved difficult. Now a new study has provided what several experts called the most solid evidence yet.
The study found that older adults who had lost 10 to 19 teeth were more likely than those who had lost fewer teeth to have a major risk factor for stroke — plaque clogging the main arteries to the brain.
A leading theory for the connection between the teeth and the arteries is that periodontal disease, a bacterial infection of the gums, may start a cascade of chemical events that cause inflammation throughout the body.
Chronic inflammation in the arteries is thought to contribute to atherosclerosis, a narrowing of blood vessels that can lead to stroke or heart attack.
“The underlying hypothesis is that chronic inflammation contributes to coronary artery disease,” said Dr. Ann Bolger, an associate professor of medicine at the University of California at San Francisco and a spokeswoman for the American Heart Association, which is publishing the new study in the September issue of Stroke, one of its journals.
The new study followed 711 people ranging in age from about 57 to 75 who had no history of stroke or heart attack. The researchers scanned their carotid arteries, the major blood vessels on either side of the neck, for evidence of atherosclerosis, and examined their teeth and gums.
The researchers looked for signs of periodontal disease by such conventional measures as plaque on the teeth and pockets between the teeth and gums. They also counted the number of teeth each person had and considered tooth loss to be an indicator of past periodontal disease.
“People lose teeth due to dental caries and periodontal disease,” said Dr. Panos N. Papapanou, director of the division of periodontics at Columbia University School of Dental and Oral Surgery and a researcher on the study. “The theory is that the older you are, the more teeth are lost for periodontal reasons.”
The study found that the people with the most missing teeth had the most severe periodontal disease, but missing teeth correlated with carotid artery plaque only up to a point.
The prevalence of carotid artery plaque was lowest — 44 percent, on average — among the people who were missing 9 or fewer teeth. By contrast, the prevalence of carotid artery plaque was 61 percent, on average, among the people who were missing 10 to 19 teeth. But the prevalence was 57 percent among people with 20 to 31 missing teeth.
Dr. Moise Desvarieux, the lead author of the study, said he did not know why the incidence of carotid artery plaque leveled off in people who had lost 20 or more teeth.
“If you have very few teeth left, it may be that the tooth loss is not related to periodontal disease but to something else,” said Dr. Desvarieux, an assistant professor of epidemiology and medicine at the University of Minnesota.
One of the difficulties in studying the relationship between gum disease and coronary artery disease is that the two conditions share many risk factors, like smoking, diabetes and high blood pressure.
An unanswered question has been whether these other risk factors account for most or all of the association previously seen between gum disease and coronary artery disease. But when the new study controlled for these risk factors, it still found that carotid artery plaque was most common in people who had lost 10 to 19 teeth.
A weakness of the study is that it did not find a correlation between periodontal disease itself and the incidence of carotid artery plaque, said Dr. Kaumudi J. Joshipura, an associate professor of oral health policy and epidemiology at the Harvard School of Dental Medicine.
“It’s not clear what to make of the fact that tooth loss was associated with carotid artery plaque and periodontal disease was not,” said Dr. Joshipura, who published a study in January that showed an association between tooth loss, periodontal disease and stroke in 41,380 men who participated in the Health Professionals Follow-Up Study, a continuing health research project.
No study has shown that gum disease or tooth loss actually causes stroke, heart disease or atherosclerosis. But Dr. Desvarieux and his colleagues will continue following the people in their study over the next three years to see if they can find a cause-and-effect relationship.
“We will compare people with higher versus lower incidence and look at the progression of carotid artery thickness and the incidence of heart attacks and strokes,” Dr. Desvarieux said. “We will also look at the microbiology and inflammation locally and in the blood.”
An important chemical that they will look for in the blood is C-reactive protein, a byproduct of inflammation, which in elevated levels indicates an increased risk of heart attack.
The long-term goal is to see if people can protect their hearts and their brains by taking good care of their teeth.
“One of the advantages of looking at gum infections is that they’re preventable and treatable,” Dr. Desvarieux said.