Periodontal disease, or gum disease, is also known as "periodontitis" and it is caused by infection and inflammation of the gums. It affects many adults and it is particularly common among seniors. According to the Centers for Disease Control and Prevention (CDC), gum disease affects over 70 percent of people aged 65 and above in the United States.
Although the CDC note that this disease affects more men than women, a significant proportion (38.4 percent) of the adult female U.S. population live with periodontitis.
Recent research has shown that women with gum disease are also more likely to develop breast cancer. However, until now, no studies had looked at the impact of periodontitis on cancer risk more generally.
Jean Wactawski-Wende, Ph.D., from the State University of New York at Buffalo - in collaboration with colleagues from other U.S. institutions - has, for the first time, investigated the association between gum disease and several types of cancer in women.
The study confirmed previous findings, but it also revealed previously undetected connections, such as the link between gum disease and gallbladder cancer. The findings are published in the journal Cancer Epidemiology, Biomarkers & Prevention.
Periodontitis increases overall cancer risk
To understand the correlation between periodontal disease and the risk of cancer in women, the researchers worked with a cohort of 65,869 female participants from the Women's Health Initiative Observational Study. The women were aged between 54 and 86, and most of them were white, non-Hispanic.
The participants reported their gum disease diagnoses through questionnaires between 1999 and 2003, and they were monitored for cancer detection up until September 2013.
On average, the follow-up period for each participant was of 8.32 years. At the end of this period, 7,149 women had been diagnosed with a form of cancer.
The researchers found that women who had reported a diagnosis of periodontal disease had a 14 percent higher risk of developing any type of cancer.
Esophageal cancer was the type most frequently associated with gum disease, as women with periodontitis were more than three times likelier to develop it compared with women without oral health problems.
"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," explains Dr. Wactawski-Wende.
Association with gallbladder cancer reported
The association between periodontitis and gallbladder cancer was a new discovery, according to the researchers.
Lead author Dr. Ngozi Nwizu, from the University of Texas School of Dentistry in Houston, TX, emphasizes the importance of this finding.
"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."
Dr. Wactawski-Wende and her colleagues also found a strong link between gum disease and breast cancer, lung cancer, and gallbladder cancer in the case of women who smoked. Especially significant, according to Dr. Nwizu, were the verdicts on gallbladder cancer and cancer of the esophagus.
Esophageal cancer still has no known causes, so the researchers hope that this will be the first step in gaining a better understanding of its formation.
"Esophageal cancer ranks among the most deadly cancers and its etiology is not well known, but chronic inflammation has been implicated," says Dr. Nwizu. The next step, she suggests, will be to determine whether bacteria linked to gum disease also play a role in inflammation related to esophageal cancer:
"Certain periodontal bacteria have been shown to promote inflammation [...], and these bacteria have been isolated from many organ systems and some cancers including esophageal cancers. It is important to establish if periodontal disease is an important risk of esophageal cancer, so that appropriate preventive measures can be promoted."
Underlying mechanisms remain mysterious
What exactly causes the link between periodontitis and various types of cancer is yet to be understood. One explanation offered by the researchers is that bacteria and other pathogens from the mouth might make their way into the bloodstream through saliva or diseased gum tissue.
In this way, pathogens could reach various parts of the body and be involved in the process of cancer formation. However, more research needs to be carried out in this direction to establish the actual mechanism at play.
The researchers acknowledge that their study faced some limitations - mainly the fact that the data used for the analysis were self-reported by the participants, so they may not have been entirely accurate.
Nevertheless, Dr. Wactawski-Wende and her colleagues place their confidence in the extensive size of the population sample, emphasizing the comprehensiveness of their study and the impact of their novel findings.
"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," conclude the researchers.