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"Our study was sufficiently large and detailed enough to examine not just overall risk of cancer among older women with periodontal disease, but also to provide useful information on a number of cancer-specific sites," said the study's senior author Jean Wactawski-Wende, Professor at University at Buffalo, New York. 

The study included 65 869 postmenopausal women enrolled in the Women's Health Initiative, an ongoing national prospective study designed to investigate factors affecting disease and death risk in older American women. 

The average age of the participants was 68, and most were non-Hispanic white women.

As part of a follow-up health questionnaire, participants were asked "Has a dentist or dental hygienist ever told you that you had periodontal or gum disease?"

Women who reported a history of gum disease had a 14 per cent increased risk of overall cancer, according to the study published in the journal Cancer Epidemiology, Biomarkers & Prevention.

The risk associated with periodontal disease was highest for esophageal cancer, the researchers reported. 

"The esophagus is in close proximity to the oral cavity, and so periodontal pathogens may more easily gain access to and infect the esophageal mucosa and promote cancer risk at that site," Wactawski-Wende said.

Gallbladder cancer risk also was high in women who reported a history of gum disease.

"Chronic inflammation has also been implicated in gallbladder cancer, but there has been no data on the association between periodontal disease and gallbladder risk. Ours is the first study to report on such an association," said Ngozi Nwizu, Assistant Professor at the University of Texas Health Science Center at Houston.

Nwizu worked on the research while completing her doctorate in pathology at University at Buffalo.

The esophageal and gallbladder cancer findings are significant, Nwizu said. 

"Esophageal cancer ranks among the most deadly cancers and its etiology is not well known, but chronic inflammation has been implicated," she said.