Association of periodontitis with gastrointestinal tract disorders: A bidirectional Mendelian randomization study

The bidirectional link of periodontitis (PD) and gastrointestinal tract (GIT) disorders has been investigated in previous epidemiological studies; however, the conclusions still remain controversial. The aim of this study was to comprehensively explore the bidirectional causal effect between PD and various GIT diseases.Based on summary-level data of genome-wide association studies (GWASs), a two-sample bidirectional Mendelian randomization (MR) study was undertaken. Single-nucleotide polymorphisms (SNPs) associated with PD or GIT disorders (chronic gastritis [CG], gastric ulcer [GU], duodenal ulcer [DU], gastroesophageal reflux disease [GERD], irritable bowel syndrome [IBS], and diverticular disease of the intestine [DI]) in GWASs were applied as exposure. The primary method employed was the inverse-variance weighted (IVW) method, and several sensitivity analyses were performed to investigate potential pleiotropy.With regard to the investigation of the causality between PD and GIT disorders, the IVW method revealed that there is a causal impact of PD on GU (odds ratio [OR] 1.088; 95% confidence interval [CI], 1.036-1.141; adjusted p = 0.004) and DI (OR 0.938; 95% CI, 0.911-0.965; adjusted p = 0.000). However, no significant genetic liability was observed for the causal effect of PD on CG, DU, GERD, and IBS. Furthermore, the primary analysis did not demonstrate a causal effect of GIT disorders on PD.This MR study suggests that PD may be associated with an increased risk of GU and a reduced risk of DI, with possibly limited clinical relevance. Further studies are needed to support the conclusions of this MR study.