According to a study published in the June edition of The Lancet Oncology, gum disease raises a person's overall risk of getting cancer - independent of whether or not the person is a smoker or not.

Gum infections result in increased concentrations of inflammatory markers that circulate in their blood. Researchers are not entirely sure, however, if systemic inflammation (pathogenic invasion into the bloodstream) or the immune system's response to gum infection affects tumors sites and overall cancer risk.

To investigate possible associations, Dr Dominique Michaud (Imperial College London, UK) and colleagues analyzed data from the Health Professionals Follow-Up study (HFPS), a survey beginning in 1986 that was targeted to US male health professionals ages 40 to 75 and managed by the Harvard University School of Public Health, USA. After participants responded to baseline questionnaires, living participants responded to follow-up questionnaires every two years and dietary questionnaires every four years. In addition to information on smoking history and food intake, participants were asked to report on baseline gum disease with bone loss, number of natural teeth, and tooth loss in the previous two years. Follow-up questionnaires also collected data on any new cancer diagnoses, helping researchers focus on the endpoints of overall cancer risk and individual cancers having more than 100 cases.

Of the 48,375 men (median follow-up of 17.7 years) who were eligible for the study, 5720 cases of cancer were recorded - not including non-melanoma skin cancer and non-aggressive prostate cancer. Of the most popular cancers, there were:
1043 colorectal cancers, 698 cases of melanoma of the skin, 678 lung cancers, 543 bladder cancers, 541 advanced prostate cancers. The researchers found that after adjusting for details about the history of smoking, dietary factors, and other known risk factors, participants with a history of gum disease were 14% more likely to develop any type of cancer compared to those without history of gum disease.

Looking at specific cancer sites, those with a history of gum disease had the following increases in cancer risk compared to those without a history of gum disease:
Lung cancer (36%), Kidney cancer (49%), Pancreatic cancer (54%), Hematological (white blood cell) cancers (30%). Additional analyses found a 70% increase in the risk of lung cancer for patients who had fewer teeth at baseline (from 0 to 16) compared to individuals with 25 to 32 teeth at baseline. In people who have never smoked, gum disease was predicted to increase their overall cancer risk by 21% and their risk of blood cancers by 35%. However, never-smoking did not seem to affect their risk of lung cancer.

"Gum disease was associated with a small, but significant, increase in overall cancer risk, which persisted in never-smokers. The associations recorded for lung cancer are probably because of residual confounding by smoking. The increased risks noted for haematological, kidney, and pancreatic cancers need confirmation, but suggest that gum disease might be a marker of a susceptible immune system or might directly affect cancer risk," conclude the authors.

Periodontal disease, tooth loss, and cancer risk in male health professionals: a prospective cohort study
Dominique S Michaud, Yan Liu, Mara Meyer, Edward Giovannucci, Kaumudi Joshipura
The Lancet Oncology (2008); 9[6]: pp. 550-8.
DOI:10.1016/S1470-2045(08)70106-2
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: Peter M Crosta