[Effect of transcutaneous auricular vagus nerve stimulation on nocturnal autonomic nervous function in primary...

To observe the effect of transcutaneous auricular vagus nerve stimulation (taVNS) on the sleep quality and nocturnal heart rate variability (HRV) in patients with primary insomnia.

Twenty-one patients with primary insomnia were included. Using SDZ-ⅡB electric acupuncture apparatus, Xin (CO₁₅) and Shen (CO₁₀) were stimulated with disperse-dense wave, 4 Hz/ 20 Hz in frequency, (0.2±30%) ms of pulse width and tolerable intensity. Electric stimulation was given once every morning and evening of a day, 30 min each time, for 4 weeks totally. Before and after treatment, the score of Pittsburgh sleep quality index (PSQI), objective sleep structure (total sleep time [TST], sleep latency [SL], wake after sleep onset [WASO], sleep efficiency [SE], the percentages of non-rapid eye movement period 1, 2, 3, and the percentage of rapid eye movement period to TST [N1%, N2%, N3%, REM%] ) and nocturnal HRV (high frequency [HF], low frequency [LF], the ratio of LF to HF [LF/HF], standard deviation for the normal RR intervals [SDNN], squared root of the mean sum of squares of differences between adjacent intervals RR [RMSSD], the percentage of adjacent RR intervals with differences larger than 50 ms in the entire recording [PNN50%], the mean of sinus RR intervals [NNMean] ) were compared in the patients separately.

After treatment, the score of each item and the total score of PSQI and SL were all reduced as compared with those before treatment (P<0.01, P<0.001); SE, N3%, LF, HF, LF/HF, SDNN, NNMean and RMSSD were all increased compared with those before treatment (P<0.001, P<0.01).

The taVNS improves the sleep quality and objective sleep structure in patients with primary insomnia, which is probably related to the regulation of autonomic nervous functions.