Bidirectional associations between periodontitis and inflammatory bowel disease: A systematic review of longitudinal studies with meta‐analysis and trial sequential analysis

The bidirectional associations between periodontitis and inflammatory bowel disease (IBD) with temporal directionality remain inconclusive. This study aims to evaluate the bidirectional associations between periodontitis and IBD through a systematic review and meta‐analysis. Five databases (PubMed, Embase, Web of Science, Scopus and Cochrane Library) were systematically searched from inception to 27 February 2024. Two independent reviewers performed a review of the retrieved studies. Longitudinal studies, including cohort and nested case–control studies, were considered eligible for the study design. The pooled risk ratio (RR) and hazard ratio (HR) derived from the meta‐analysis were used to assess whether periodontitis (or IBD) was a risk factor for IBD (or periodontitis). Trial sequential analysis (TSA) was performed to evaluate the reliability of the results. Four studies (n = 10 270 912) on the risk of IBD in patients with periodontitis and two (n = 33 420) on the risk of periodontitis in patients with IBD were included. The result suggested that periodontitis did not increase the risk of IBD (pooled RR = 1.04, 95% confidence interval [CI]: 0.99–1.09; p = .164; I‐squared statistic [I2] = 27%). For subtypes of IBD, periodontitis was associated with the occurrence of ulcerative colitis (UC) (pooled RR = 1.12, 95% CI: 1.04–1.21; p = .003; I2 = 38%), but not with Crohn's disease (CD) (pooled RR = 0.98, 95% CI: 0.92–1.04; p = .475; I2 = 0%). Specifically, the risk of UC was higher among men (pooled HR = 1.11, 95% CI: 1.01–1.22; p = .025; I2 = 0%) and smokers (pooled HR = 1.23, 95% CI: 1.07–1.42; p = .004; I2 = 0%) with periodontitis than their counterparts without periodontitis. Patients with IBD may have a higher risk of developing periodontitis (pooled HR = 1.37, 95% CI: 1.26–1.49; p