Investigating a Causal Relationship Between Diabetes Mellitus and Oropharyngeal Cancer: A Mendelian Randomization Study.

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.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).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.Our findings suggest little evidence to support the genetic role of diabetes mellitus in OPC development in the European population.