For me, it's been one of the more surprising observations in recent years: study after study has shown that people who have poor oral health (such as gum disease or tooth loss) have higher rates of cardiovascular problems such as heart attack or stroke than people with good oral health.

Why would cardiovascular disease and poor oral health be connected?

A number of theories have been proposed, including:

The bacteria that infect the gums and cause gingivitis and periodontis also travel to blood vessels elsewhere in the body where they cause blood vessel inflammation and damage; tiny blood clots, heart attack and stroke may follow. Supporting this idea is the finding of remnants of oral bacteria within atherosclerotic blood vessels far from the mouth. Then again, antibiotic treatment has not proven effective at reducing cardiovascular risk.

Rather than bacteria causing the problem, it's the body's immune response – inflammation - that sets off a cascade of vascular damage throughout the body, including the heart and brain.

There may be no direct connection between gum disease and cardiovascular disease; the reason they may occur together is that there is a 3rd factor (such as smoking) that's a risk factor for both conditions. Other potential "confounders" include poor access to healthcare and lack of exercise – perhaps people without health insurance or who don't take good care of their overall health are more likely to have poor oral health and heart disease.

A recent study is among the largest to look at this question. Researchers analyzed data from nearly a million people who experienced more than 65,000 cardiovascular events (including heart attack) and found that:

After accounting for age, there was a moderate correlation between tooth loss (a measure of poor oral health) and coronary heart disease.

When smoking status was considered, the connection between tooth loss and cardiovascular disease largely disappeared

This study suggets that the observed connection between poor oral health does not directly cause cardiovascular disease. But if that's true, how do we explain other studies that found a connection even after accounting for smoking and other cardiovascular risk factors?

It's rare that a single study definitively answers a question that has been pondered by researchers for decades. So, we'll probably need additional studies to sort this out.

But wait, there's more!

The connection between poor oral health and overall health may not be limited to cardiovascular disease. Studies have linked periodontal disease (especially if due to infection with a bacterium called porphyromonas gingivalis) and rheumatoid arthritis. In addition, a 2016 study found a link between this same bacterium and risk of pancreatic cancer. However, as in the case of the connection with heart disease, an "association" is not the same as causation; we'll need additional research to figure out the importance of these observations.

The bottom line

Whether the link is direct, indirect or coincidence, a healthy mouth and a regimen to keep it that way (including not smoking, and getting regular dental care) can help you keep your teeth. That's reason enough to do what you can to make oral health a priority. Perhaps it will turn out to have other benefits though much of that remains speculative.

Stand by for more studies on the link between oral health and overall health. Until then, keep brushing, flossing and seeing your dentist.

— Robert H. Shmerling, MD

Robert H. Shmerling, MD, is associate professor of medicine at Harvard Medical School and Clinical Chief of Rheumatology at Beth Israel Deaconess Medical Center in Boston where he teaches in the Internal Medicine Residency Program. He is also the program director of the Rheumatology Fellowship. He has been a practicing rheumatologist for over 25 years.

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