Smokers in particular are vulnerable
Women with periodontal disease have a higher risk of developing breast cancer, especially if they’re smokers or recently quit smoking, a recent study shows.
“We have seen associations between periodontal disease and chronic diseases, including stroke and heart attacks,” said Jo Freudenheim, professor and interim chair of the epidemiology and environmental health department at the University at Buffalo. “Our hypothesis was that it would also be associated with breast cancer. 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.”
The study, published in Cancer Epidemiology, Biomarkers & Prevention, analyzed 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 breast cancer risk.
“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,” said study co-author 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.”
Previously, three small studies examined the possible link between periodontal disease and breast cancer, and all three showed a non-statistically significant increase in risk. Because this study was much larger, it was possible to examine the association more closely and look at how smoking impacted the 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 said. “These bacteria may influence diseases that were previously thought to have no infectious component.”
Researchers say there are multiple possible causes for the connection:
- Bacteria from the oral cavity can get into the bloodstream after tooth brushing, flossing and chewing. Though these bacteria are cleared quickly, there is 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.
- Other factors, which increase both the risk of periodontal disease and breast cancer, may be present.
“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 it will reduce cancer,’” Freudenheim said. “We are now learning a huge amount about the microbiome, the bacteria, viruses and other microorganisms that share our world. 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.”