Exploring the link between oral health and heart health

Despite the wide availability of drugs to treat associated risk factors, cardiovascular disease remains the second-leading cause of death in Canada. It accounts for 20 per cent of all deaths, equaling one death every seven minutes. Maria Febbraio, a medical researcher in the Department of Dentistry, believes this means there must be other contributing factors to heart disease that haven’t been identified. Febbraio, who is also a member of the Women and Children's Health Research Institute, is working with a team of researchers on one possible culprit that might be right under our noses: periodontal disease.

In the 1990s, researchers started to investigate the link between periodontal disease and heart disease. Thanks to the availability of databases around the globe with thousands of patients coded for heart disease and periodontal disease, researchers noticed a relationship between the two conditions. “There were a lot of epidemiological studies published around that time that showed how the people with bad periodontal disease also had increased atherosclerosis — hardening of the arteries — and heart disease,” explains Febbraio. 

Periodontal diseases are mainly the result of infections and inflammation of the gums and bone that surround and support the teeth. In 2012, the American Heart Association recognized that periodontal disease is an independent risk factor in heart disease. However, the exact mechanism between the two conditions is unknown.

What is known is that inflammation of tissue is involved. “Inflammation underlies heart disease,” says Febbraio, “and periodontal disease increases inflammation.” Even when inflammation is only in the gums, it affects the rest of the body in three possible ways. 

The first possible way is that periodontal disease caused by bacteria in your oral cavity may travel and take up residency in the arteries and the heart, where it causes local inflammation. 

A second possibility is that brushing your teeth while having active periodontal disease causes gums to bleed, resulting in bacteria entering the bloodstream. The body’s immune response to this bacterial invasion is inflammation.  

The third possibility is that the inflammation may be only in your gums, but cytokines and chemokines — proteins that are involved in your body’s immune response — are systemic, so they affect your whole body.  

“There's evidence that all three of those things occur with periodontal disease,” says Febbraio, “and that's how it increases overall systemic inflammation and causes this disease.”

Febbraio points out that like quitting smoking, treating periodontal disease doesn’t immediately eliminate the risk of health complications. You still have an elevated risk of heart disease for a period of time following the successful treatment of periodontal disease. “So that means that the risk must be stored somewhere because you no longer have the risk factor. So where are you storing the response to that risk factor once it's gone?” she asks. “That’s the part we’re interested in: the long-term effects of this inflammation.”  

Through research using animal models, Febbraio’s team has observed that atherosclerosis can be passed by bone marrow transplant to mice that have never had periodontal disease. They suspect this is because inflammation as a result of periodontal disease causes progenitor cells —  the stem cells in the bone marrow — to undergo a change in their DNA due to a process called methylation. Methylation can cause a specific gene to be activated or inactivated, and may explain why the effects of periodontal disease continue in the body long after the risk factor has been eliminated. “Our results suggest that a risk factor can persist after we eliminate it due to changes in expression of genes as a result of methylation changes in DNA,” says Febbraio. 

Understanding the mechanisms behind the persistence of risk factors is important, because it will allow for the development of new therapies. In the meantime, there is some hope from existing treatment options. “The good news is methylation changes are also observed in cancer and liver disease,” says Febbraio, “so there are drugs currently available and more are being researched.”

The research into the connection between periodontal disease and heart disease may be complex, but Febbraio suggests that preventing both could be quite simple. “Do what your parents and your dentist have always told you: Brush your teeth at least twice a day, floss at least once a day and go to the dentist at least twice a year to get your teeth cleaned by a professional, especially as you age.”