Transcutaneous Auricular Vagus Nerve Stimulation in Insomnia: A Systematic Review and Meta-Analysis.

Objectives: Insomnia is a prevalent condition with significant impacts on quality of life, often accompanied by anxiety and depression. Transcutaneous auricular vagus nerve stimulation (taVNS) has emerged as a noninvasive therapeutic option, but its efficacy and mechanisms remain to be fully elucidated. This systematic review and meta-analysis aimed to evaluate the clinical effectiveness of taVNS on insomnia, as measured by the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI).

Materials and methods: We systematically searched PubMed, Embase, and the CENTRAL data bases up to January 2025 for clinical trials comparing taVNS in patients with insomnia. This study followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Statistical analyses were performed using R version 4.3.2. The risk of bias was assessed using the Risk Of Bias In Non-randomized Studies - of Interventions and Risk Of Bias in Randomized Studies tools, and the quality of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) assessment. The study was registered in the International Prospective Register of Systematic Reviews under protocol CRD42025634016.

Results: Of 313 studies screened, six met the inclusion criteria and were included, encompassing a total of 336 patients. The pooled analysis showed statistically significant improvements in sleep quality and insomnia severity, as measured by PSQI (MD = -3.60; 95% CI = -4.98 to -2.22; p < 0.01; GRADE = Low evidence) and ISI (MD = -5.24; 95% CI = -9.02 to -1.46; p < 0.01; GRADE = Very low evidence) scores. Moreover, the studies reported improvements in sleep subscales, including overall sleep quality, latency, duration, and efficiency. Adverse effects were minimal and manageable, highlighting the safety profile of taVNS and supporting its potential as a well-tolerated, noninvasive treatment option for insomnia.

Conclusion: taVNS can significantly relieve insomnia, supported by its neural and autonomic pathways modulation. These findings highlight taVNS as a promising, safe, and noninvasive treatment for insomnia, warranting further research to optimize its application and expand its use in broader populations.