NEW YORK (Reuters Health) - Gum disease may increase the risk of developing deadly pancreatic cancer, even among those who have never smoked, according to research reported today in Boston at the American Association for Cancer Research's Frontiers in Cancer Prevention Research Meeting.

Two previous studies found positive associations between tooth loss or periodontitis (inflammation of the gums around the teeth) and pancreatic cancer. However, "residual confounding" by smoking and other known risk factors may have accounted for the findings.

To investigate further, Dr. Dominique S. Michaud of Harvard School of Public Health, Boston and colleagues analyzed 16 years of health data on nearly 52,000 male doctors in the Health Professionals Follow-up Study. This ongoing study, initiated in 1986, is looking at lifestyle factors related to cancer and other chronic diseases.

A total of 216 men developed pancreatic cancer during follow-up. After factoring out smoking, diabetes, obesity, physical activity, diet and other potentially confounding factors, men with a history of gum disease had a 63-percent higher risk of developing pancreatic cancer relative to men without periodontal disease.

Never smokers with gum disease fared even worse; "they had 2-fold increased risk in developing pancreatic cancer," Michaud told a gathering of reporters Monday.

"This is an important finding," Dr. Scott Lippman of The University of Texas M. D. Anderson Cancer Center in Houston said, noting that there have been a couple of small reports that "just dismissed" the gum disease/pancreatic cancer link as potentially related to smoking, given that smoking increases the risk of pancreatic cancer.

"This (new) study is the first clearly establishing the increased risk of pancreatic cancer with periodontal disease," regardless of smoking history, Lippman said.

Michaud's team also found that men with gum disease and recent tooth loss had a 2.7-fold increased risk of developing pancreatic cancer compared with those who reported neither gum disease nor tooth loss.

Periodontal disease may boost the risk of pancreatic cancer through "plausible mechanisms," Michaud and colleagues point out in meeting materials.

Gum disease results in chronic inflammation over many years, they explain, and people with gum disease harbor high levels of harmful bacteria in the mouth and gut and tend to have higher amounts of cancer-causing nitrosamines.

Pancreatic cancer, the fourth leading cause of death from cancer death in the United States, is one of the most deadly cancers, largely because it is often not detected until it has spread beyond the pancreas. Only about five percent of pancreatic cancer patients survive the first five years after being diagnosed.