Tooth loss and periodontal disease have previously been associated with several cancers, and poor oral health may be an important risk factor for upper gastrointestinal (i.e. esophageal and gastric) cancers in high-risk areas.

In this study, we assessed the relationship between oral health and upper gastrointestinal cancers using a large prospective study of more than 50,000 adults (40-75 years old) living in Golestan Province in northeast of Iran, a high-incidence area for these cancers. Participants in Golestan Cohort Study were recruited from January 2004 to June 2008, and oral health was assessed in detail by trained interviewers. We used Cox proportional hazards regression models to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association between three different measures of oral health (the number of missing teeth, the sum of decayed, missing, and filled teeth (DMFT), and the frequency of tooth brushing) and incident esophageal and gastric cancers.

During a median follow-up duration of 12 years until January 31, 2019, there were 342 and 354 incident cases of esophageal and gastric cancer, respectively. Excess tooth loss was significantly associated with the risk of esophageal cancer (HR = 1.61; 95% CI: 1.10, 2.37) but not gastric cancer (HR = 1.25; 95% CI: 0.85, 1.85). Daily tooth brushing was associated with decreased risk of developing both esophageal (HR = 0.75; 95% CI: 0.53, 1.05) and gastric (HR = 0.64; 95% CI: 0.45, 0.90) cancers. There was no significant association between DMFT and either upper gastrointestinal cancer.

These results suggest increased risk of developing esophageal and gastric cancers among individuals with poor oral health, and those who do not have regular oral hygiene practices.