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

Abstract

Objective: Insomnia disorder is a common condition with considerable harmful effects on health. We investigated the therapeutic efficacy 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 insomnia 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 μg/dL vs. -0.16±3.49 μg/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 hypothalamic-pituitary-adrenal axis activity.

Keywords: Cortisol; Electrical stimulation; Insomnia; Sleep quality; Transcutaneous electric nerve stimulation.

Figure 1.

Flowchart of study participants. LF-TENS, low-frequency transcutaneous electric nerve stimulation.

Figure 2.

The positive treatment rate among study participants. A: Overall participants. B: Elderly participants (aged >60 years). C: Middle-aged participants (aged 40–60 years). ^*p<0.05.

Figure 3.

Individual distribution of the elderly patients aged >60 years with and without positive treatment response according to the reduction in Pittsburgh Sleep Quality Index (PSQI) score after intervention. A: The reduction in PSQI score after intervention in those with active treatment. B: The reduction in PSQI score after intervention in those with sham treatment.