Postmenopausal women with periodontal disease were more likely to develop breast cancer than women without chronic inflammatory gum disease, according to a study published in Cancer Epidemiology, Biomarkers & Prevention, a publication of the American Association for the Study of Cancer.

 Periodontal disease is a common condition and has been shown to be associated with heart disease, stroke and diabetes,” says lead author Jo L. Freudenheim, PhD, Distinguished Professor in the Department of Epidemiology and Environmental Health in the School of Public Health and Health Professions at the University at Buffalo. Previous research has revealed links between periodontal disease and oral, esophageal, head and neck, pancreatic and lung cancers, so we wanted to see if there was a link to breast cancer.”

Periodontal disease is a common condition and has been shown to be associated with heart disease, stroke and diabetes,” says lead author Jo L. Freudenheim, PhD, Distinguished Professor in the Department of Epidemiology and Environmental Health in the School of Public Health and Health Professions at the University at Buffalo.

“Previous research has revealed links between periodontal disease and oral, oesophageal, head and neck, pancreatic and lung cancers, so we wanted to see if there was a link to breast cancer.” Freudenheim and colleagues monitored 73,737 postmenopausal women enrolled in the Women’s Health Initiative Observational Study, none of whom had breast cancer. Periodontal disease was present in 26.1% of the women. Because previous studies have shown that the effects of periodontal disease differ if the person smokes, the researchers examined stratified associations based on smoking or non-smoking status.

After an average of 6 to 7 years, 2,124 women were diagnosed with breast cancer. The researchers found that among all women, the risk of breast cancer was 14% higher in women with periodontal disease. Among women who had quit smoking in the past 20 years, those with periodontal disease had a 36% higher risk of 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.

Women who had never smoked or who had quit more than 20 years ago had a 6% and 8% higher risk respectively if they had periodontal disease. The highest risk was found for women smokers who had quit within the last 20 years. This could indicate that previous exposure to smoking has affected the carcinogenic process and that the effects of smoking are hardly reversible. The bacteria in the mouths of smokers or recent quitters are different from those in the mouths of non-smokers. There are several possible explanations for the link between periodontal disease and breast cancer.

1. A systemic inflammation with periodontal disease affecting breast tissue.
2. Bacteria from the mouth can enter the circulatory system, potentially affecting breast tissue.

Further studies are needed to establish a causal link. “If we could study periodontal disease and breast cancer in other populations and if we could do more detailed studies on the characteristics of periodontal disease, it would help us understand if there is a link,” Freudenheim said. “There is still much to be understood about the role, if any, of oral bacteria and breast cancer. “One limitation of the study is that the women self-reported the presence of periodontal disease after being asked if a dentist had ever told them they had it.

Also, since this study was designed for women who were already enrolled in a long-term national health study, they were more likely to receive regular medical and dental care and were more lifestyle-conscious than the majority of the population. Freudenheim estimated that the percentage of the population suffering from periodontal disease and other risk factors such as smoking, diabetes and obesity would be higher.[Cancer Epidemiol Biomarkers Prev. 2016 Jan;25(1):43-50. doi: 10.1158/1055-9965. EPI-15-0750. Epub 2015 Dec 21.]

Periodontal Disease and Breast Cancer: Prospective Cohort Study of Postmenopausal Women.Freudenheim JL1, Genco RJ2, LaMonte MJ3, Millen AE3, Hovey KM3, Mai X3, Nwizu N4, Andrews CA5, Wactawski-Wende J3.