Inflammatory Bowel disease promote oral cancer and pharyngeal cancer: new evidence of Mendelian randomization

Evidence from observational studies shows that inflammatory bowel disease (IBD) [comprising ulcerative colitis (UC) and Crohn’s disease (CD)] is a risk factor to Oral cavity and pharyngeal cancer (OC&amp;PC) [comprising Oral cavity cancer (OCC) and Oropharyngeal cancer (OPC)], but it is unclear whether these diseases have potential causality. We aimed to explore the causal relationship between IBD and OC&amp;PC. A mendelian randomized (MR) study was performed to estimate the causal relationship between IBD and OC&amp;PC. The potential causal relationship was statistically significant between IBD and OCC (OR = 1.14, 95% confidence interval (CI): 1.02–1.27, <i>p</i> = .02), UC and OCC (OR = 1.13, 95% CI: 1.01–1.27, <i>p</i> = .03), respectively. There was a universal null effect of IBD on OC&amp;PC (IBD: OR = 1.01, 95%CI: 0.93–1.10, <i>p</i> = .74; UC: OR = 1.00, 95%CI: 0.92–1.10, <i>p</i> = .94; CD: OR = 1.02, 95%CI: 0.94–1.09, <i>p</i> = .69), and IBD on OPC (IBD: OR = 0.93, 95%CI: 0.81–1.06, <i>p</i> = 0.26; UC: OR = 0.90, 95%CI: 0.79–1.03, <i>p</i> = .12; CD: OR = 1.04, 95%CI: 0.94–1.15, <i>p</i> = .44). MR analyses support new evidence indicating there may be a positive causal effect of IBD (including UC) on OCC. Further investigation of the potential biological mechanisms is necessary.