A large Harvard University analysis over 20 years found that poor dental hygiene increases the risk of throat and stomach cancer by up to 43% and 52% respectively.
The Daily Telegraph reports that the research found the risk was even higher among those who had previously lost teeth, the research found. Gum disease has previously been found to lead to heart problems as bacteria spread through the blood.
But the new research, by scientists from the Harvard TH Chan School of Public Health, looked at oesophageal and gastric cancer rates in 98,459 women and 49,685 men over a period of more than 20 years.
Dental measures, demographics, lifestyle, and diet were assessed using follow-up questionnaires and self-reported cancer diagnosis was confirmed after reviewing medical records. The results showed that during 22 to 28 years of follow up, there were 199 cases of oesophageal cancer and 238 cases of gastric cancer.
The report says a history of gum disease was associated with a 43% and 52% increased risk of oesophageal cancer and gastric cancer, respectively, the study found. Compared to people with no tooth loss, the risks of oesophageal and gastric cancer for those who lost two or more teeth were also modestly higher – 42% and 33%, respectively.
Those with a history of gum disease, and who may or may not have had tooth loss, were equally linked with a 59% increased risk of oesophageal cancer compared to those with no history of periodontal disease and no tooth loss. Those with a history of gum disease and no tooth loss had a 50% increased risk of gastric cancer, which rose to 68% for those with a history of gum disease and tooth loss, compared to those with no history and no loss.
The findings could help doctors to pinpoint patients who would be at greater risk of these cancers in the future, the researchers said.
The report says a link between bacteria commonly found in the mouth – such as that tannerella forsythia and porphyromonas gingivalis – and oesophageal cancer has been made by other scientists in previous studies.
Another possible reason is that poor oral hygiene and gum disease could promote the formation of bacteria known to cause gastric cancer, scientists said.
In this study, the large sample size, long term follow-up of the patients, and “rigorous control” for lifestyle impacts, adds strength to the findings, Dr Mingyang Song, Harvard TH Chan School of Public Health is quoted in the report as saying.
The authors concluded: “Together, these data support the importance of oral microbiome in oesophageal and gastric cancer. “Further prospective studies that directly assess oral microbiome are warranted to identify specific oral bacteria responsible for this relationship.”
Chun-Han Lo, Sohee Kwon, Liang Wang, Georgios Polychronidis, Markus D Knudsen, Rong Zhong, Yin Cao, Kana Wu, Shuji Ogino, Edward L Giovannucci, Andrew T Chan, Mingyang Song
Full report in The Daily Telegraph
BMJ Gut letter