Efficacy and safety of transcutaneous auricular vagus nerve stimulation (ta-VNS) in the treatment of tinnitus: protocol for an updated systematic review and meta-analysis

Introduction With an increasing incidence and significant effects on patients, tinnitus has become a major disease burden. There is a dearth of therapies with established efficacy for tinnitus. Transcutaneous auricular vagus nerve stimulation (ta-VNS) is being investigated as a potential therapy for tinnitus, but the current body of evidence remains inconclusive due to conflicting results across different studies. As a result, this protocol aims to synthesise and update the evidence to clarify whether ta-VNS is effective and safe for alleviating tinnitus. Methods and analysis To identify relevant randomised controlled trials (RCTs), seven representative bibliographical databases will be searched from their inception to December 2023: PubMed, Embase (via OVID), Cochrane Library, Chinese National Knowledge Infrastructure, Wangfang Database, Chinese BioMedical Literature Database, and Chongqing VIP Chinese Science and Technology Periodical Database. Publications in English or Chinese will be considered for inclusion. RCTs comparing ta-VNS with active treatments, no intervention, waitlist control or sham ta-VNS in adult patients with subjective tinnitus will be included. Studies on objective tinnitus will be excluded. Primary outcome is tinnitus symptom severity measured by validated scales. With all eligible trials included, when applicable, quantitative analysis via meta-analyses will be performed using RevMan V.5.4.1 software. Otherwise, a qualitative analysis will be conducted. The methodological quality of the included RCTs will be assessed using the Risk of Bias 2.0 tool. Sensitivity analyses, subgroup analysis and publication bias evaluation will also be performed. The Grading of Recommendations, Assessment, Development, and Evaluation approach will be used to grade the certainty of the evidence. Ethics and dissemination Ethical approval is not required for this systematic review, as no primary data will be collected. The results will be reported and disseminated through publication in a peer-reviewed journal. PROSPERO registration number CRD42022351917.