Age-Limited Effects of Low-Frequency Transcutaneous Electric Nerve Stimulation on Insomnia: A 4-Week Multi-Center, Randomized Controlled Study

Objective Insomnia disorder is a common condition with considerable harmful effects on health. We investigated the therapeutic effi-cacy and safety of low-frequency transcutaneous electric nerve stimulation (LF-TENS) as an alternative treatment option for insomnia disorder. Methods A 4-week, multi-center, randomized controlled study was conducted. A total of 160 individuals aged 40 to 80 years with in-somnia disorder were included and randomized to the experimental group receiving active device (n=81) or control group receiving sham device (n=79). Both groups used the device for four weeks, more than five days a week. The participants also completed pre-and post-intervention assessment with questionnaires, sleep diaries, wrist actigraphy, and blood tests. Results There was no significant between-group difference in the changes of mood and sleep parameters and blood test results among the two study groups. Meanwhile, in the exploratory sub-group analysis of patients aged over 60 years, the experimental group showed better improvement after intervention in the change of Pittsburgh Sleep Quality Index (PSQI) score (-2.63 +/- 3.25 vs.-1.20 +/- 2.28, p=0.039; Cohen's d=0.99 vs. 0.45) and blood cortisol level (-1.65 +/- 3.37 mu g/dL vs.-0.16 +/- 3.49 mu g/dL, p=0.007; Cohen's d=0.56 vs. 0.05). In addition, no serious adverse reaction occurred during the study period in both groups. Conclusion The effect of LF-TENS was limited to older patients aged over 60 years, which might be related to the modulation of hypo-thalamic-pituitary-adrenal axis activity. Psychiatry Investig 2022;19(6):451-461