Women who report having periodontal disease are at greater risk for breast cancer, especially if they smoke or recently quit smoking, a new study reports.
“We have seen associations between periodontal disease and chronic diseases including stroke and heart attacks. Our hypothesis was that it would also be associated with breast cancer,” says Jo Freudenheim, professor and interim chair of the epidemiology and environmental health department at the University at Buffalo.
“We thought that periodontal bacteria—either the bacteria themselves or the inflammation that’s part of having periodontal disease—has an effect on other parts of the body, including breast tissue. We know there are bacteria in breast tissue and we know there’s bacteria in mother’s milk. Women who had periodontal disease had a small increase in the risk of breast cancer overall,” she says.
For a study published in Cancer Epidemiology, Biomarkers & Prevention, researchers examined self-reported data from more than 73,000 postmenopausal participants in the Women’s Health Initiative, a federally funded long-term study that started in 1991. The women were followed to determine who was diagnosed with breast cancer. Among women who were smokers or who had quit smoking in the previous 20 years, those with periodontal disease had a 36 percent higher risk of breast cancer.
“Up to this point, we’ve known very little about the association between poor oral health and breast cancer, especially among smokers, who are more likely to have periodontal disease,” says coauthor Robert Genco, a professor of oral biology.
“What we’re seeing is an association between periodontal disease and breast cancer in a large and well-designed study. Since periodontal disease affects half or more women in this age range, the increase in risk, although small, may be important on a population base.
Further study of mechanism and effects of periodontal intervention are necessary to more fully understand this relationship.”
Previously, only three small studies have been conducted examining the link between periodontal disease and breast cancer, and all three showed a non-statistically significant increase in risk. Because this study was such a large one, it was possible to examine the association more closely and look at how smoking affected the observed relationship.
“There’s been an explosion of information recently that makes it clear that many different parts of the body that were thought to be sterile contain bacteria and other microbes,” Freudenheim says. “These bacteria may influence diseases that were previously thought to have no infectious component.”
Researchers say there are several possible causes for the linkage:
- Bacteria from the oral cavity can get into the bloodstream following tooth brushing, flossing, and chewing. These bacteria are cleared quickly; however, there is considerable cumulative exposure to tissues. It could be that these microbes affect breast cancer.
- Inflammation in one part of the body may have an impact on other chronic diseases.
- It may also be that there are other factors which increase both the risk of periodontal disease and breast cancer.
“This is a new area, so we have to be careful in how we interpret our findings. We can’t say, ‘if you treat periodontal disease that it will reduce cancer,’” Freudenheim says. “We are now learning a huge amount about the microbiome, the bacteria, viruses, and other microorganisms that share our world.
“There are new methodologies that allow us to measure things we weren’t able to before. We are now beginning to understand how much the interaction of the microbiome affects our health both in terms of acute infections and chronic diseases.”
Other researchers from the University at Buffalo and from the University of Texas Health Science Center at Houston School of Dentistry, and the University of Michigan are coauthors of the work.