Associations of oral health with colorectal cancer risk: accumulated evidences from observational studies.

PURPOSE: This study aimed to systematically evaluate the associations between oral health conditions, including periodontitis, tooth loss, and dental caries, and colorectal cancer (CRC) risk.

MATERIALS AND

METHODS

PubMed, Embase, the Cochrane Library, Web of Science, Scopus, and Google Scholar were searched from inception to January 12, 2026 for observational studies assessing oral health conditions in relation to CRC risk. Adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) were pooled for the primary meta-analysis. Subgroup analyses were conducted according to sex, smoking status, diagnostic method, tumor location, geographic region, and adjustment quality to explore potential sources of heterogeneity. Sensitivity analyses included leave-one-out analysis to assess the robustness of the findings. A dose-response analysis was performed to evaluate the association between the number of missing teeth and CRC risk. Study quality was assessed using the Newcastle-Ottawa Scale (NOS).

RESULT: A total of 15 studies were included. Periodontitis was associated with an increased risk of CRC (HR = 1.24, 95% CI: 1.04-1.48; I2= 83.53%). Subgroup analyses revealed substantial variability across study characteristics, with no significant associations observed in sex-specific or non-smoking populations, and stronger associations in studies using administrative claims-based definitions. The association remained significant among studies with higher adjustment quality. In contrast, tooth loss was not significantly associated with CRC risk (HR = 1.08, 95% CI: 0.98-1.19; I2= 28.85%), and no significant association was observed for dental caries (HR = 1.10, 95% CI: 0.91-1.32; I2= 0%). Dose-response analysis showed no significant association between the number of missing teeth and CRC risk (per 10 teeth: HR = 1.03, 95% CI: 0.96-1.10). Sensitivity analyses confirmed the robustness of the findings, and no significant publication bias was detected.

CONCLUSION

Periodontitis is associated with an increased risk of CRC, whereas current evidence does not support significant associations for tooth loss or dental caries. Given the observational nature of the included studies and the presence of heterogeneity, these findings should be interpreted with caution. Further well-designed prospective cohort studies are warranted to clarify the relationship between oral health and CRC risk.