Brushing and flossing are a must for keeping plaque off your teeth and gums. But having a healthy mouth may have other benefits: it could also help lower your risk of dying of cancer.
Researchers at the Karolinska Institute and the University of Helsinki report in the British Medical Journal Open that people with high levels of dental plaque were 80% more likely to die prematurely of cancer during a 24-year study period than people with little plaque.
“The results surprised us a lot,” says lead author Birgitta Soder of the department of dental sciences at the Karolinska Institute.
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Soder and her colleagues randomly selected 1,390 people to participate in the study beginning in 1985. All of the volunteers came in for a dental exam, and the researchers recorded the amount of plaque, tartar, gum disease and tooth loss they had. People who showed signs of periodontal disease were excluded. The participants then filled out questionnaires detailing behaviors that can influence cancer risk, such as smoking.
By the end of the study, 4.2% had died of cancer, and when the scientists compared the amount of dental plaque in those who had died to those who survived, they found a significantly higher amount among the deceased. The association held strong even after the researchers accounted for factors that can contribute to both cancer risk and dental health, such as smoking, income level and education.
The average age of death for women was 61, and for men 60. Considering that the women would have been expected to live about 13 years longer, according to demographic data, and the men an additional 8.5 years, their deaths could be considered premature, the authors note.
Soder had some idea that the link between dental plaque and cancer would be worth studying; in a previous trial, she found that women who had more plaque were more likely to develop breast cancer. The reason for the link probably has something to do with inflammation. Thousands of species of bacteria live in our mouths, and persistent plaque — made up of a thin film of bacteria, which covers the surface of teeth and accumulates between teeth and gums — can increase the chances of infection. That, in turn, can trigger the body’s immune system to launch a defense in the form of an inflammatory reaction, which sends enzymes and other chemicals into the bloodstream that can push vulnerable cells to divide recklessly and form tumors. Up to 20% of cancers are driven by some inflammatory process.
Inflammation may also explain why periodontal disease, a condition in which the gums become chronically infected, is linked with heart disease. Scientists think inflammatory factors triggered by gum infections can spread from the mouth throughout the bloodstream, affecting the heart, although studies investigating the connection have been mixed.
Based on this first analysis, Soder can’t conclude that bad oral hygiene actually causes cancer; the data are only observational. But the association suggests that plaque could be a contributing factor in people with existing genetic predispositions to cancer. “We don’t know if dental plaque could be a real causal part of cancer,” Soder says. “But it is a little scary to see that something we all have in our mouths can play such a role.”
That’s something to remember the next time you feel like dropping off to sleep without bothering to brush or floss.