Postmenopausal women with periodontal disease are more likely to develop breast cancer than women who do not have the chronic inflammatory disease. A history of smoking significantly affects this risk. These findings were published in Cancer Epidemiology, Biomarkers & Prevention (doi:10.1158/1055-9965.EPI-15-0750).

Periodontal disease is associated with heart disease, stroke, and diabetes. Previous research has identified links between periodontal disease and oral, esophageal, head and neck, pancreatic, and lung cancers. Researchers at the University at Buffalo [New York] School of Public Health and Health Professions sought to determine if there was a connection between this common oral condition and breast cancer.

Jo L. Freudenheim, PhD, distinguished professor in the Department of Epidemiology and Environmental Health, and colleagues monitored 73 737 postmenopausal women enrolled in the Women’s Health Initiative Observational Study, none of whom had previous breast cancer. Periodontal disease was reported in 26.1% of the women. Prior studies have shown that the effects of periodontal disease vary depending on the person’s smoking status; therefore, the researchers stratified their data by smoking status.

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After a mean follow-up time of 6.7 years, 2124 women developed breast cancer. Among all women, the risk of breast cancer was 14% higher in those with periodontal disease.

Among women who quit smoking within the past 20 years, those with periodontal disease had a 36% higher risk of developing breast cancer. Women who were smokers at the time of the study had a 32% higher risk if they had periodontal disease, but the association was not statistically significant. Among those who had never smoked and those who had quit more than 20 years ago, the risk of developing breast cancer was increased 6% and 8%, respectively, if they had periodontal disease.

“We know that the bacteria in the mouths of current and former smokers who quit recently are different from those in the mouths of nonsmokers,” explained Freudenheim.

One possible explanation for this link is that those bacteria enter the body’s circulation and ultimately affect breast tissue. However, further studies are needed to establish a causal link.

A study limitation was that periodontal disease status was self-reported after the women were asked whether a dentist had ever told them they had the condition. In addition, the study focused on women who were already enrolled in a long-term national health study, therefore they were more likely than the general population to be receiving regular medical and dental care, and were likely more health-conscious than the general population.

Funding for this study was provided by the National Heart, Lung and Blood Institute, the National Institutes of Health, and the US Department of Health and Human Services.