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Are You at Risk for Stroke? Better Count Your Teeth...

Preserving a healthy smile may be more important than you think. According to a recent study published in Stroke: Journal of the American Heart Association, tooth loss and periodontal disease may increase the risk of ischemic stroke, the most common type of stroke suffered by Americans. Periodontal disease is the result of bacteria in tooth plaque, which causes gum erosion and inflammation. This study adds to the growing body of evidence that infection and inflammation play a role in stroke and heart disease. It also shows a striking link between tooth loss and stroke. In the study, men with fewer than 25 teeth had a 57 percent higher risk of ischemic stroke than those with more than 25 teeth. Below, Kaumudi J. Joshipura, BDS, Sc.D., a lead investigator on the study, and associate professor of epidemiology at Harvard School of Dental Medicine, talks about the significance of the study, and what it might one day mean for your own dental hygiene.

What were the findings of this study?
There is a lot of medical literature relating chronic bacterial infections to cardiovascular disease and stroke. We wanted to know if periodontal disease and tooth loss-which is partly a consequence of periodontal disease-were risk factors for ischemic stroke. We studied over 40,000 men, who were all health professionals, over the course of twelve years. We evaluated the periodontal disease and tooth loss and then followed them for twelve years to see how many of them developed stroke. And we found that men with 24 teeth or less had a 57% higher risk of stroke than men with 25 or more teeth. We also found a 33% increase risk of stroke associated with periodontal disease.

Isn't there a chance that people with fewer teeth or periodontal disease are more likely to have other risk factors that would naturally put them at risk for stroke?
There are many common risk factors for periodontal disease, tooth loss and ischemic stroke, such as smoking, socioeconomic status, diabetes, exercise, diet and smoking. It is important to be able to separate out these factors and to be able to see an association independent of these factors. This is why it is helpful to have a homogenous group of health professionals, with a more consistent, high spectrum of healthy behavior. They're likely to do more things to help their cardiovascular health and dental health. So there's less variation, and this helps control for some of the factors related to behavior, which we can measure as well as factors that we cannot measure.

So compared to other studies, we feel more confident in this kind of population than if it was a general population. But even within the group that we studied, there's still some variation. We try to control for it as best we can when analyzing the data and, by using this homogenous group, that gives an additional measure of control.

Did any results of the study surprise you?
What was surprising is that the association between tooth loss and stroke is actually stronger among nonsmokers than smokers.

What does that mean?
It just makes us confident that the association isn't due to smoking alone.

Why would bacterial infection put people at risk of cardiovascular disease and stroke?
There are several potential reasons that have been proposed. The bacteria itself may go into the bloodstream, which could cause damage to the cells lining the blood vessels, which is one of the first things that could trigger a stroke or cause heart disease.

The other possibility is that toxic proteins from the bacteria stimulate the production of certain inflammatory markers which contribute to developing these problems.

And of course the other consideration is the common risk factors, including common genetic factors. So somebody may just be predisposed to inflammatory disease. Nobody has, as yet, tried to control for genetic factors (when doing this type of study); so there could just be some kind of gene that predisposes you to inflammatory disease, which could lead to heart disease or stroke.

Do these results imply that prevention of periodontal disease and tooth loss will help prevent ischemic stroke?
I would say at this stage we do not know if preventing periodontal disease and tooth loss would actually reduce the risk of stroke or not. But given that we don't know for sure, it doesn't hurt to take better care of your teeth, and do your best to prevent and control periodontal disease and also practice good preventive behavior for cardiovascular health as well.

If it is determined that there is a causal relationship between periodontal disease and stroke, what might change in dental health?
People would have to go for more regular scaling, root planing, and sometimes have medical therapy to control the bacteria; whatever it takes to decrease the disease.