Is there a genetic correlation between tinnitus and temporomandibular joint disorder?: A two-sample Mendelian randomization study

Tinnitus and temporomandibular disorder (TMD) are frequent coexistence of clinical symptoms caused by some systemic diseases in all humans. The observational research results on the correlation between tinnitus and TMD are inconsistent with the reported findings. The purpose of the study was to explore the bidirectional causal relationship between tinnitus and TMD. This study adopts a two-sample Mendelian randomization (MR) methodology. Single-nucleotide polymorphisms from the genome-wide association study were used as instrumental variables to elucidate the bidirectional causal relationship between tinnitus and TMD. The quality of our study was evaluated in accordance with the STROBE-MR guidelines. The MR analysis results showed that tinnitus (yes, most or all of the time now) could be significantly reduced TMD muscular pain linked with fibromyalgia (OR = 0.239, 95% CI: 0.087-0.66, P = .0057), but there was no correlation between other frequencies of tinnitus and the increased risk of TMD in genetic predisposition (all P > .05). The reverse MR analysis revealed no causal relationship and correlation between TMD exposure and increased risk of tinnitus. Sensitivity analysis indicated no horizontal pleiotropy and insignificant heterogeneity. This MR study supports evidence of a correlation between high-frequency tinnitus and reduced risk of TMD muscle pain associated with fibromyalgia. Further research on disease mechanisms are needed to explore the correlation between tinnitus and TMD.