Transcutaneous Auricular Vagus Nerve Stimulation for Chronic Insomnia Disorder

IMPORTANCE: Evidence from randomized clinical trials of transcutaneous auricular vagus nerve stimulation (taVNS) for chronic insomnia disorder is lacking. OBJECTIVE: To evaluate the efficacy and safety of taVNS for chronic insomnia compared with the sham taVNS. DESIGN, SETTING, and PARTICIPANTS: This randomized clinical trial was conducted from October 2021 to December 2022 at a single center in Beijing, China. Patients with chronic insomnia disorder with a Pittsburgh Sleep Quality Index (PSQI) of at least 8 were enrolled. Statistical analysis was performed from June to September 2023. INTERVENTIONS: Patients were allocated to the active taVNS group or sham taVNS group with a 1:1 ratio. Both groups received the stimulation for 30 minutes each time, twice a day, 5 consecutive days a week, with an 8-week treatment and a 12-week follow-up. MAIN OUTCOMES AND MEASURES: The primary end point was the mean change from baseline through week 8 in PSQI scores. Minimal clinically important difference was 2.5 points. Secondary outcomes included mental health, sleepiness, and fatigue. Safety was also evaluated. RESULTS: A total of 72 participants were randomized to either active taVNS group (36 participants; mean [SD] age, 45.2 [14.5] years; 27 [75.0%] female) or the sham taVNS group (36 participants; mean [SD] age, 44.6 [13.9] years; 31 [86.1%] female); 68 participants completed the 8-week intervention. The least-square mean changes from baseline to week 8 in PSQI were -8.2 (95% CI, -9.3 to -7.0) points in the taVNS group and -3.9 (95% CI, -5.1 to -2.7) points in the sham group. Both groups experienced statistically significant improvements from before to after the intervention. However, active taVNS showed a clinically meaningful 4.2-point greater reduction (95% CI, -5.9 to -2.6 points; P < .001; Cohen d effect size, 1.2) in PSQI compared with the sham group (minimal clinically important difference = 2.5 points). Secondary outcomes, including mental health and fatigue, showed similar favorable results. The efficacy of taVNS was sustained throughout the 20-week study period. CONCLUSIONS AND RELEVANCE: In this randomized clinical trial, taVNS significantly reduced insomnia severity. Clinically meaningful enhancements in PSQI scores were observed compared with sham stimulation, with the benefits of taVNS sustained over a 20-week period. Future multicenter clinical trials with large sample sizes are needed to validate its effectiveness across diverse populations. Trial Registration: Chinese Clinical Trial Registry: ChiCTR2100051319.