Background The association between oral hygiene—specifically, tooth brushing and tooth loss—and gastric cancer (GC) incidence risk remains inconclusive. Previous meta-analyses are outdated and insufficient in exploring heterogeneity. To address this gap, this study aims to perform an updated and comprehensive evaluation of this association. Methods We systematically searched PubMed, Embase, Web of Science, Scopus, and the Cochrane Library up to April 2024 for studies examining tooth brushing frequency, tooth loss, and GC risk. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a random-effects model. Heterogeneity was assessed and explored via meta-regression and subgroup analysis. Results Twelve studies were included. Infrequent tooth brushing was associated with a 55% increased GC risk (OR 1.55, 95% CI: 1.17–2.05). Despite significant heterogeneity, largely attributable to study design, this association was robust in sensitivity analyses. Tooth loss also significantly increased GC risk (OR 1.25, 95% CI: 1.12–1.39). Notably, subgroup analyses identified geographic region as a key source of heterogeneity, with the tooth loss-associated risk being substantially stronger in Europe and America (OR 1.68) than in Asia (OR 1.19) populations. Sensitivity analyses supported the robustness of these findings. Conclusion This study solidifies poor oral hygiene as a significant risk factor for GC. The marked geographic disparity offers novel insights for developing targeted primary prevention strategies, underscoring the importance of integrating oral health into general cancer prevention initiatives. Systematic review registration http://www.crd.york.ac.uk/prospero , identifier: CRD42024546658.
Ge et al. (Fri,) studied this question.