RESUMEN
BACKGROUND: 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&PC) [comprising Oral cavity cancer (OCC) and Oropharyngeal cancer (OPC)], but it is unclear whether these diseases have potential causality. OBJECTIVES: We aimed to explore the causal relationship between IBD and OC&PC. MATERIALS AND METHODS: A mendelian randomized (MR) study was performed to estimate the causal relationship between IBD and OC&PC. RESULTS: The potential causal relationship was statistically significant between IBD and OCC (OR = 1.14, 95% confidence interval (CI): 1.02-1.27, p = .02), UC and OCC (OR = 1.13, 95% CI: 1.01-1.27, p = .03), respectively. There was a universal null effect of IBD on OC&PC (IBD: OR = 1.01, 95%CI: 0.93-1.10, p = .74; UC: OR = 1.00, 95%CI: 0.92-1.10, p = .94; CD: OR = 1.02, 95%CI: 0.94-1.09, p = .69), and IBD on OPC (IBD: OR = 0.93, 95%CI: 0.81-1.06, p = 0.26; UC: OR = 0.90, 95%CI: 0.79-1.03, p = .12; CD: OR = 1.04, 95%CI: 0.94-1.15, p = .44). CONCLUSIONS AND SIGNIFICANCE: 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.