Here's yet another reason to floss, and to end the baffling distinction that health insurers make between our mouths and the rest of our bodies:
A big study of more than 7,000 people out in the Journal of the National Cancer Institute reports that people found to have severe gum disease had a 24 percent higher risk of cancer compared with those with mild or no gum disease.
You might look to cigarettes for the explanation — smoking increases both the risk of gum disease and of cancer — but the researchers adjusted for smoking and still found higher cancer risk from severe gum disease alone.
I spoke with lead author Dominique Michaud of the Tufts University School of Medicine. Our edited conversation:
How would you sum up what you found?
This was the largest study looking at the association between gum disease and overall cancer risk that used dental exams to measure and classify severity of gum disease.
In this study, we found that individuals with severe gum disease had a 24 percent higher risk of developing cancer compared to those with no or mild gum disease. The association was strongest for lung cancer as well as for colorectal cancer.
These associations were observed after controlling not just for age and sex and race but also for smoking, which is very important because some studies have not done that, and it could be a confounder.
How does this add to what we already know about the link between gum disease and cancer?
The evidence now is quite strong. I was talking about flossing and pancreatic cancer about 10 years ago, when my first study was published in the Journal of the National Cancer Institute. A lot has happened in the past 10 years, and the evidence is building to a case that's quite strong.
Where this study is really important is in the fact that we had the dental exams. Many of the previous studies, including the one that was published 10 years ago, used self reports. In this study, we had all the participants take part in a dental examination that was conducted specifically for this study. And the status of their gum disease was known for everyone at baseline.
What are the policy implications?
Obviously, this is an observational study, so the causal mechanisms — understanding how the gum disease causes the cancer, and whether there's a direct causal link — still need to be figured out and understood.
But I think it's not too early to say that we really need to jump on this opportunity to reduce cancer burden by really making a push for better dental insurance coverage to include especially those who are most vulnerable to developing severe gum disease.
Who's considered most vulnerable?
People who are of lower socioeconomic status, who are not taking good care of their teeth or have no access to dentists. Also people who smoke tend to have a higher risk of developing gum disease.
And what would you say to people who are thinking right now, "Yikes, I have gum disease, that means I'm at increased risk of cancer"?
Just because we find an association doesn't mean that you're going to develop cancer if you have gum disease. The association is not as strong as, for example, smoking and lung cancer, where there's a very strong association.
Out of all the people who have gum disease — because it's a very large percentage of the population — only a very small percentage will develop cancer. We need to do more research on figuring out who are those people who are going to develop cancer.
And the absolute risk of developing cancer in your study was small, right?
It was very small. The 24 percent higher risk is just a relative risk.
And these findings add to the absurdity of thinking about dental health as separate from our physical health, right?
I agree with you that it is completely ridiculous, because there is so much evidence. Cancer is just one of the outcomes that are linked to gum disease, but there are many others — diabetes, stroke, possibly premature birth. There's a growing amount of data showing how important your mouth is, and how it's connected to so many other things in your body. It's a gateway. It has a huge impact on the immune response.
So the health in your mouth will have a lot of repercussions, cancer being one of them but there are many others. It makes no sense to me either that dental care should not be part of general health insurance because it is very, very much tied to so many chronic conditions. There are just a lot of things that could be prevented if only we had dental insurance as part of health insurance.
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