The study, reported in the Journal of the National Cancer Institute, said men with periodontal disease had a 63 percent higher risk of developing pancreatic cancer than men with healthy teeth and gums. And men who lost teeth within the past four years were especially likely to develop pancreatic cancer.

    While the study does not definitively show gum disease causes cancer, the researchers say the evidence is strong. They filtered out other factors known to be linked with pancreatic cancer, such as smoking and obesity.

    "Most convincing was our finding that never-smokers (with gum disease) had a two-fold increase in risk of pancreatic cancer," said Dominique Michaud of the Harvard School of Public Health, who led the study.

    Michaud's team studied 48,000 men taking part in the Health Professionals Follow-Up Study between 1986 and 2002. These men, aged 40 to 75 at the start, answered a battery of questions about health and lifestyle and were then watched to see which diseases they developed.

    More than half the men are dentists.

    On the baseline questionnaire, participants responded to the following question: "Have you had periodontal disease with bone loss?"

    Pancreatic cancer is the fourth-leading cause of cancer deaths in the United States. It will kill 95 percent of the 32,000 people who get it this year, according to the American Cancer Society.

    It is not usually diagnosed until it is far advanced, and thus ways to identify people at high risk might save lives.

    "Our study provides the first strong evidence that periodontal disease may increase the risk of pancreatic cancer. This finding is of significance as it may provide some new insights into the mechanism of this highly fatal disease," Michaud said in a statement.

    Periodontal disease is caused when bacteria infect the gums and the infection gradually destroys bone. Other studies have found a link between gum disease or tooth loss and pancreatic cancer, but did not account for smoking -- which can cause both gum disease and pancreatic cancer.

    In this study, the effects of gum disease appeared to affect non-smokers more than smokers, the researchers found.

    Michaud said the study is not proof.

    "More research is needed both to confirm this finding in other populations and also to explore the role of inflammation in this particular cancer," she said.

    "The association may be due to systemic (throughout the body) inflammation and/or increased levels of carcinogenic compounds generated by bacteria in the oral cavity of individuals with periodontal disease," the researchers wrote.

    The men with gum disease seemed to have chronic inflammation -- their levels of a protein called C-reactive protein, a measure of inflammation, were 30 percent higher than those of men with healthy gums.

    Or the bacteria responsible for the gum loss could produce nitrosamines, which are compounds known to cause cancer.

    "Individuals with periodontal disease and poor oral hygiene have elevated levels of oral bacteria and have much higher nitrosamine levels in their oral cavity," the researchers wrote.

    (Agencies)