Bidirectional Mendelian randomization between oral microbiota and allergic rhinitis in East Asian populations.

Objective: To investigate the bidirectional causal associations between genetically predicted oral microbial taxa and allergic rhinitis (AR) in East Asian populations. Methods: We used summary-level genome-wide association study (GWAS) data from East Asian populations to conduct a bidirectional two-sample Mendelian randomization (MR) analysis. The inverse-variance weighted (IVW) method was the primary method. Bayesian weighted Mendelian randomization (BWMR) was used to assess the robustness of taxa that remained significant after IVW-based FDR correction. Cochran's Q test, the MR-Egger intercept test, and MR-PRESSO were used to assess heterogeneity and horizontal pleiotropy. Results: In the forward MR analysis, 16 tongue dorsum and 22 salivary microbial taxa were associated with AR risk. BWMR supported associations for 15 tongue dorsum and 17 salivary taxa, with effect directions generally consistent with those obtained using IVW. Representative associations included a positive association between genetically predicted salivary Campylobacter_A_mgs_1095 abundance and AR risk (OR = 1.381), and an inverse association between tongue dorsum Streptococcus_mgs_1057 abundance and AR risk (OR = 0.767).Sensitivity analyses indicated no substantial heterogeneity or horizontal pleiotropy for most taxa. Conclusions: Genetically predicted abundances of several tongue dorsum and salivary microbial taxa were associated with AR risk in East Asian GWAS datasets.These findings require validation in larger independent cohorts and experimental studies.