December 2023

Objective: Previous observational studies reported an association of diabetes mellitus (DM) with oropharyngeal cancer (OPC), however, the potential causality of the association between them remains unclear. Methods: To explore this causal relationship in individuals of European descent, a two-sample Mendelian randomization (MR) study was conducted. A genome-wide association study (GWAS) of DM was used to represent the exposure factor (T1DM: n = 24,840; T2DM: n = 215,654), and GWAS of OPC represented the outcome (n = 3,448). Results: Forty-one single nucleotide polymorphisms (SNPs) related to T1DM and fifty-four SNPs related to T2DM were identified as effective instrumental variables (IVs) in the two-sample MR analyses. In IVW estimates, neither T1DM nor T2DM significantly contributed to an increased risk of OPC [T1DM: OR 1.0322 (95% CI 0.9718, 1.0963), P = 0.3033; T2DM: OR 0.9998 (95% CI 0.9995, 1.0002), P = 0.2858]. Four other regression models produced similar results. MR-Egger regression results [Cochran’s Q statistic was 47.1544 (P = 0.1466) in T1DM, and 35.5084 (P = 0.9512) in T2DM] suggested no horizontal pleiotropy between IVs and outcomes. Conclusion: Our findings suggest little evidence to support the genetic role of diabetes mellitus in OPC development in the European population. Keywords: single nucleotide polymorphisms, diabetes mellitus, oropharyngeal cancer, Mendelian randomization, genome-wide association study