Vagus Nerve Stimulation Enhances Sleep Quality

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Results of a randomized clinical trial showed transcutaneous auricular vagus nerve stimulation (taVNS) significantly reduced insomnia severity among patients with chronic insomnia disorder. The improvements, especially in Pittsburgh Sleep Quality Index (PSQI) scores, were clinically meaningful compared with sham stimulation and were sustained over a 20-week period, demonstrating both the safety and efficacy of taVNS.

The taVNS intervention is a nonpharmacological method that has been effective in treating migraine, depression and epilepsy. In recent years, the modality has gained attention in the treatment of insomnia by improving sleep quality while alleviating anxiety, depression, fatigue and daytime sleepiness.

Insomnia, with common symptoms including excessive sleepiness, mood and cognitive disturbances, fatigue and other issues with sleep, affects approximately one in three adults worldwide. The main treatment options for this condition are cognitive behavioral therapy and medications. However, side effects from medication — such as dizziness, memory issues, dexterity impairments and drowsiness — coupled with coordination concerns surrounding therapy training and scheduling led researchers to want to develop new treatment approaches.

“Previous studies have demonstrated that taVNS cannot only effectively improve sleep quality in patients with insomnia, but also alleviate accompanying symptoms such as anxiety, depression, daytime sleepiness and fatigue,” wrote lead investigator Shuai Zhang, M.D., Ph.D., of the Institute of Acupuncture and Moxibustion at the China Academy of Chinese Medical Sciences.

The trial, called the Transcutaneous Auricular Stimulation with Chronic Insomnia (TASC-I), evaluated the safety and efficacy of taVNS for treating chronic insomnia disorder.

Participants received either active or sham taVNS for eight weeks with 12 weeks of follow-up at the Acupuncture and Moxibustion Hospital, China Academy of Chinese Medical Sciences (CACMS), between October 2021 and December 2022. Investigators theorized the protocol would provide greater improvements in sleep severity after the intervention period.

The main end point was the change in PSQI score — which measures sleep quality using seven components for the features of sleep — from baseline to week 8. Minimal important change is considered 4 points from baseline. Secondary end points evaluated the Hamilton Depression Scale (HAMD), the Hamilton Anxiety Scale (HAMA), the Epworth Sleepiness Scale (ESS) and the Flinders Fatigue Scale (FSS).

Of the 72 patients enrolled in the study, 36 were placed in the taVNS cohort and 36 were randomly assigned to the control group. At baseline, no differences in variables were observed between groups.

Among the taVNS cohort, significant improvements in sleep quality were observed, with a clinically meaningful reduction of 8.2 points in PSQI scores compared with a 3.9-point reduction in the sham group.

Secondary outcomes, such as mental health and fatigue, also improved. Results suggest that taVNS is a safe and effective treatment for chronic insomnia, with benefits sustained over time.

Investigators noted they were unable to confirm the effect of different stimulation intensities on clinical efficacy as they used the maximum tolerable high intensity during the study period. Additionally, although the intervention was linked to sleep severity improvements at week 4, they were comparable to those of the sham cohort at week 20. Therefore, investigators theorize additional improvements may happen later, leading them to call for future research to assess the long-term clinical efficacy of taVNS as well as to identify an optimal treatment regimen for patients with insomnia.

“This study adds to the growing body of evidence supporting taVNS as a promising nonpharmacological intervention for chronic insomnia disorder,” wrote investigators.