Novel Risk Loci in Tinnitus and Causal Inference With Neuropsychiatric Disorders Among Adults of European Ancestry

Importance Tinnitus affects at least 16 million US adults, but its pathophysiology is complicated, and treatment options remain limited. A heritable component has been identified in family and twin studies; however, no large-scale genome-wide association studies (GWAS) have been accomplished. Objective To identify genetic risk loci associated with tinnitus, determine genetic correlations, and infer possible relationships of tinnitus with hearing loss and neuropsychiatric disorders and traits. Design, Setting, and Participants A GWAS of self-reported tinnitus was performed in the UK Biobank (UKB) cohort using a linear mixed-model method implemented in BOLT-LMM (linear mixed model). Replication of significant findings was sought in the nonoverlapping US Million Veteran Program (MVP) cohort. A total of 172995 UKB (discovery) and 260832 MVP (replication) participants of European ancestry with self-report regarding tinnitus and hearing loss underwent genomic analysis. Linkage-disequilibrium score regression and mendelian randomization were performed between tinnitus and hearing loss and neuropsychiatric disorders. Data from the UKB were acquired and analyzed from September 24, 2018, to December 13, 2019. Data acquisition for the MVP cohort was completed July 22, 2019. Data analysis for both cohorts was completed on February 11, 2020. Main Outcomes and Measures Estimates of single nucleotide variation (SNV)-based heritability for tinnitus, identification of genetic risk loci and genes, functional mapping, and replication were performed. Genetic association and inferred causality of tinnitus compared with hearing loss and neuropsychiatric disorders and traits were analyzed. Results Of 172 995 UKB participants (53.7% female; mean [SD], 58.0 [8.2] years), 155 395 unrelated participants underwent SNV-based heritability analyses across a range of tinnitus phenotype definitions that explained approximately 6% of the heritability. The GWAS based on the most heritable model in the full UKB cohort identified 6 genome-wide significant loci and 27 genes in gene-based analyses, with replication of 3 of 6 loci and 8 of 27 genes in 260 832 MVP cohort participants (92.8% men; mean [SD] age, 63.8 [13.2] years). Mendelian randomization indicated that major depressive disorder had a permissive effect (beta = 0.133;P = .003) and years of education had a protective effect (beta = -0.322,P = <.001) on tinnitus, whereas tinnitus and hearing loss inferred a bidirectional association (beta = 0.072,P = .001 and beta = 1.546,P = <.001, respectively). Conclusions and Relevance This large GWAS characterizes the genetic architecture of tinnitus, demonstrating modest but significant heritability and a polygenic profile with multiple significant risk loci and genes. Genetic correlation and inferred causation between tinnitus and major depressive disorder, educational level, and hearing impairment were identified, consistent with clinical and neuroimaging evidence. These findings may guide gene-based diagnostic and therapeutic approaches to this pervasive disorder. Question What is the genetic architecture of tinnitus and its association with neuropsychiatric disorders? Findings This genome-wide association study in 172995 European adults from the UK Biobank identified 6 significant loci and 27 genes, with replication in 260832 adults from the Million Veteran Program for 3 of 6 loci and 8 of 27 genes. Genetic correlations were identified between tinnitus and hearing loss, insomnia, and neuropsychiatric disorders, and evidence of relationships based on mendelian randomization was inferred for major depressive disorder, years of schooling, and hearing loss. Meaning Characterization of the genetic architecture of tinnitus and identification of specific risk genes is critical for targeted clinical research into this pervasive disorder. This genome-wide association study with mendelian randomization identifies genetic risk loci associated with tinnitus, determines genetic correlations, and infers relationships of tinnitus with hearing loss and neuropsychiatric disorders and traits.