Background: Previous research indicates that poor dental health increases risks for certain types of cancers, including esophageal cancer. This study aimed to investigate the association with esophageal cancer using Swedish Dental Health Register. Methods: This is a prospective cohort study. The exposures were dental diagnoses classified into healthy, caries, root canal infection, mild inflammation, and periodontitis, as well as number of remaining teeth, at baseline and during multiple visits. The outcome was the incidence of esophageal cancer, which was further divided into esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC). Cox proportional hazards models were used to estimate hazard ratios (HRs) and its corresponding confidence intervals (CIs). Results: A total of 5,042,303 individuals were included in the study and 1,259 EAC and 758 ESCC cases were identified. Root canal infection at baseline was associated with 41% higher risk for EAC (HR=1.41, 95% CI: 1.10-1.82), while periodontitis at baseline was linked to 32% and 45% higher risks for respective histopathological subtypes (HR for EAC=1.32, 95% CI: 1.13-1.53; HR for ESCC=1.45, 95% CI: 1.20-1.75). Fewer remaining teeth at baseline also increased the risks for both histopathological types of esophageal cancer, with a dose-response effect (Ptrend < 0.01). Cox regression analyses with time-varying exposures corroborated the above-mentioned results. Conclusions: Impaired dental health prior to cancer diagnosis is associated with excess risks for both histopathological subtypes of esophageal cancer. Impact: Our study provided corroborating evidence for the association between poor oral health and esophageal cancer risk.

Background The association between atrophic gastritis (AG) and symptomatic gastroesophageal reflux disease (GERD) needs to be better assessed. Objective We aimed to study this association in a twin setting, controlling for genetic and familial factors, in addition to a range of known covariates. Methods We performed a co‐twin control study based on the Swedish Twin Registry, including confirmed monozygotic (MZ) and dizygotic (DZ) twins. AG was determined by the measurement of serum pepsinogen I (PGI) and pepsinogen II (PGII), with different cut‐off values. GERD was defined using a structured questionnaire, by questions on symptoms of heartburn, acid regurgitation, pain behind the breastbone, and drug history. Patients were grouped into total GERD, less frequent (<1/week), and frequent GERD (≥1/week). Results A total of 12,533 twins were included in the study, among whom 37.7% showed less frequent GERD, and 18.7% had frequent GERD. There was an inverse association between AG and GERD, especially for frequent GERD. When PGI<30 was used as cut‐off value for AG, the odds ratio (OR) and corresponding 95% confidence interval (CI) was 0.52 (0.44, 0.62). When PGI<70 and PGI/PGII<3 was used as cut‐off value for AG, the OR (95% CI) was 0.53 (0.46, 0.63). A risk reduction for GERD was also observed in AG patients when the analysis was restricted in MZ or DZ twins. Conclusion In this co‐twin control study from the Swedish Twin Register, AG is persistently associated with a reduced risk for GERD, after controlling for genetic and shared familial factors.