Vagus Nerve Stimulation Improves Sleep Quality, Reduces Insomnia Severity

Transcutaneous auricular vagus nerve stimulation (taVNS) significantly reduced insomnia severity, according to a small, sham-controlled trial published in JAMA Network Open.

Investigators conducted a randomized clinical trial of patients with chronic insomnia (Pittsburgh Sleep Quality Index [PSQI] ≥8) at a single center in Beijing, China, to evaluate the effect of taVNS on PSQI scores, mental health, sleepiness, and fatigue. Participants between the ages of 18 and 70 were included if they experienced insomnia for at least 3 months, at least 3 nights a week. On enrollment, participants were randomly assigned 1:1 to either the taVNS group or to a sham procedure group.

Stimulation parameters for the taVNS group included dilatational wave at 4/20 Hz, pulse width of 0.2 ms ±30%, and intensity adjusted to the patient’s maximum tolerable level (0.8-1.5 mA); those in the sham group received the same parameters with a current intensity of 0.1mA. Participants were trained to apply taVNS or sham taVNS; interventions were conducted for 30 minutes twice daily, 5 days a week for 8 weeks. Fisher exact test was employed for statistical analysis.

A total of 72 patients were included:

• taVNS group: n=36; mean age, 45.2 years (SD, 14.5); women, 75.0%
• sham taVNS group: n=36; mean age, 44.6 years (SD, 13.9); women, 86.1%

Baseline variables were similar between groups; 4 participants in the sham group and 2 participants in the taVNS group did not finish the study.

Least-squares mean change in PSQI from baseline to week 8 was –8.2 (95% CI, –9.3 to –7.0) in the taVNS group vs –3.9 (95% CI, –5.1 to –2.7) in the sham group. The taVNS group showed greater clinically meaningful reductions in total PSQI score at 8 weeks, and PSQI was significantly lower in the taVNS vs sham group (least-squares mean difference, –4.2 [95% CI, –5.9 to –2.6]; P <.001). A statistically significant improvement in PSQI was observed at week 4 in the taVNS vs sham group.

The percentage of PSQI responders (≥50% improvement from baseline) in the taVNS group at weeks 4, 8, and 20 was 50.0%, 69.4%, and 72.2%, respectively, and 16.7%, 27.8%, and 22.2%, respectively, in the sham group (ratio difference, 33.3%, 41.6%, and 50% at weeks 4, 8, and 20, respectively).

Participants in the taVNS group had a higher reduction in subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, and daytime dysfunction scores when compared with those in the sham group; no differences were observed between groups for sleep disturbances and use of hypnotic drugs.

Adverse events (AEs) occurred in 5 patients (13.9%) in the taVNS group and in 4 patients (11.1%) in the sham group; no significant differences were observed between groups for AEs. The most common taVNS-related AE was a slight clamping pain in the outer ear (taVNS, n=4; sham, n=3); the pain was resolved by local pressing and kneading of the area following treatment.

Study limitations included maximum tolerable high intensity stimulation and lack of long-term follow-up.

“During the 8-week treatment period, taVNS significantly improved patient-reported outcomes, including sleep severity, fatigue, and mental health. Notably, clinically important reductions in PSQI were observed, with sustained effects comparable to sham at the end of 20 weeks,” the authors wrote.