In a nationwide Swedish study of almost 6 million adults, researchers found that patients with poor dental health—including gum disease and fewer teeth—had a higher risk of developing gastric cancer. They tracked participants between 2009 and 2016 using national dental and cancer registers. Analyses were adjusted for education, income, alcohol- and smoking-related diseases, and family history of gastric cancer.
Over an average follow-up period of 6.36 years, 3993 participants were diagnosed with gastric cancer. Among them, 1241 had cardia gastric cancer (which affects the upper stomach near the esophagus), and 2752 had noncardia gastric cancer.
Participants with periodontitis, a severe form of gum disease, had a 25% higher risk of cardia gastric cancer compared with those who had healthy gums. The adjusted hazard ratio (HR) was 1.25 (95% confidence interval [CI] = 1.07–1.46) for cardia cancer and 1.11 (95% CI = 1.01–1.21) for all gastric cancer. The association with noncardia cancer was not statistically significant.
Tooth count was also linked to risk. Compared with patients who had more than 27 teeth, those with 14 or fewer had a 55% higher risk of gastric cancer (HR = 1.55, 95% CI = 1.36–1.76), a 70% higher risk of cardia cancer (HR = 1.70, 95% CI = 1.34–2.17), and a 49% higher risk of noncardia cancer (HR = 1.49, 95% CI = 1.28–1.74). Participants with 20 to 24 teeth had a 26% higher risk of gastric cancer (HR = 1.26, 95% CI, 1.13–1.40), and those with 14 to 20 teeth had a 46% higher risk (HR = 1.46, 95% CI = 1.30–1.64).
These findings showed a clear trend: fewer teeth correlated with greater cancer risk.
Researchers also conducted a sibling-controlled analysis of 1987 gastric cancer cases and 4022 unaffected siblings. Participants with 14 or fewer teeth had a 47% increased odds of gastric cancer (OR = 1.47, 95% CI = 1.10–1.95) compared with siblings who had more than 27 teeth. The association for periodontitis was directionally positive but not statistically significant in this sibling comparison.
No significant interaction was found between gum inflammation and tooth count, which suggested they were independent risk factors. Associations remained consistent across sex and age groups as well as in sensitivity analyses that excluded early cancer diagnoses or patients with missing data.
While the researchers did not investigate biological mechanisms directly, they noted that inflammation, oral microbiota imbalance, and chewing difficulties due to tooth loss may contribute to gastric cancer development.
“Our findings suggest that individuals with odontogenic inflammation are at higher risk of developing GC, particularly the cardia type,” wrote lead author Zengliang Ruan of the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet in Stockholm with colleagues.
The authors reported no conflicts of interest.
Source: BMC Medicine