Vagus Nerve Stimulation for Sleep Disorders: Emerging Evidence and Future Directions.

Sleep disorders are increasingly prevalent clinical conditions that significantly impair physical and mental health. Given the observed limitations of pharmacological therapies, there has been increasing research interest in effective non-pharmacological interventions. Vagus nerve stimulation (VNS), including invasive VNS and non-invasive methods such as transcutaneous auricular VNS (taVNS), has emerged as a promising neuromodulatory strategy. This review summarizes current evidence on VNS for insomnia, central hypersomnia, restless legs syndrome, and sleep-related breathing disorders, highlighting both clinical findings and proposed mechanisms. Relevant literature was identified through searches of PubMed and Web of Science up to May 2026 using terms related to VNS (eg, "vagus nerve stimulation" and "taVNS") and sleep disorders (eg, "insomnia", "narcolepsy", "hypersomnia", and "sleep-related breathing/movement disorders"). The proposed mechanisms include multilevel regulation of sleep-wake neural pathways; immunomodulation via anti-inflammatory pathways; inhibition of cortical spreading depression; and enhancement of neuroplasticity, cerebral blood flow, and blood-brain barrier integrity. Finally, we discuss key challenges regarding inter-individual variability and stimulation parameter optimization, as well as outline future directions centered on precision neuromodulation. These include the development of intelligent closed‑loop stimulation systems (ie, devices that automatically adjust stimulation parameters based on real time physiological feedback) and the testing of state dependent neuromodulation hypotheses. Taken together, this review not only summarizes current evidence but also proposes a theoretical framework and translational perspective to inform future research and clinical applications.