University at Buffalo researchers report 36 percent increase in risk among women who smoke or recently quit and have had periodontal disease
Women who report having periodontal disease are at greater risk for breast cancer, especially if they smoke or recently quit smoking, according to University at Buffalo research published in Cancer Epidemiology, Biomarkers & Prevention (CEBP), a journal of the American Association for Cancer Research.
"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," explained lead author Jo Freudenheim, UB distinguished professor and interim chair of the department of epidemiology and environmental health in UB's School of Public Health and Health Professions.
"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 said.
The 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. Researchers found that, 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," said Robert Genco, a co-author on the paper and SUNY Distinguished Professor in the department of oral biology in UB's School of Dental Medicine.
"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," Genco added.
Previously, only three small studies had 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 said. "These bacteria may influence diseases that were previously thought to have no infectious component."
There are several possible causes for the linkage, according to Freudenheim:
•Bacteria from the oral cavity 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," Freudenheim said of another possible cause.
•It may also be that there are other factors that 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 said. "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."
Co-authors include, from the department of epidemiology and environmental health in UB's School of Public Health and Health Professions: Michael J. LaMonte, research associate professor; Amy Millen, associate professor and associate chair; Kathleen Hovey, data manager/statistician; Xiaodan Mai, postdoctoral associate; and Jean Wactawski-Wende, dean and professor. Co-authors also are Ngozi Nwizu of the University of Texas Health Science Center at Houston School of Dentistry; and Christopher A. Andrews of the department of ophthalmology and visual sciences at the University of Michigan.