Effect of transcutaneous vagus nerve stimulation on daytime sleepiness, depression, and study engagement in college students: a randomized controlled trial

Many college students experience daytime sleepiness. Daytime sleepiness is reportedly associated with poor academic performance, suicide, depression, and traffic accidents. This parallel-group randomized controlled trial study aimed to examine the effect of self-care using transcutaneous vagus nerve stimulation (taVNS) in college students with sleepiness and depression. Thirty-four college students (age 21.5 ± 0.1 years, 21 men and 13 women) were assigned to a control or taVNS group. For taVNS, an electro-stimulator was used to deliver 100 Hz pulses at an intensity below each participant’s pain threshold (3.0–8.0 mV) for 30 min. taVNS was performed 30 min before bedtime every day for 28 days. Daytime sleepiness, depression, study engagement, and sleep quality were measured using the Japanese version of the Epworth Sleepiness Scale (ESS-J), Japanese version of the Beck Depression Inventory-II (BDI-II-J), Japanese version of the Utrecht Work Engagement Scale for Students (UWES-S-J), Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J), and Silmee™ Bar Type Lite. Autonomic nervous system activities were measured using high-frequency (HF) and low-frequency (LF) components of heart rate variability. Parasympathetic and sympathetic nervous system activities were indicated by the HF value and LF/HF ratio, respectively. The change in each group from day 28 to day 1 was calculated and analysed. The ESS-J, BDI-II-J, UWES-S-J, and PSQI-J (sleep quality and daytime dysfunction) scores improved, and the LF/HF ratio decreased in the taVNS group compared with the control group. Self-care using taVNS suppresses the sympathetic nervous system during sleep, which may improve sleep quality, daytime sleepiness, depression, and study engagement.