Slow oscillating transcranial direct current stimulation during sleep has a sleep‐stabilizing effect in chronic insomnia: a pilot study

Abstract

SUMMARYRecent evidence suggests that lack of slow-wave activity may play a fundamental role in the pathogenesis of insomnia. Pharmacological approaches and brain stimulation techniques have recently offered solutions for increasing slow-wave activity during sleep. We used slow (0.75 Hz) oscillatory transcranial direct current stimulation during stage 2 of non-rapid eye movement sleeping insomnia patients for resonating their brain waves to the frequency of sleep slow-wave. Six patients diagnosed with either sleep maintenance or non-restorative sleep insomnia entered the study. After 1 night of adaptation and 1 night of baseline polysomnography, patients randomly received sham or real stimulation on the third and fourth night of the experiment. Our preliminary results show that after termination of stimulations (sham or real), slow oscillatory transcranial direct current stimulation increased the duration of stage 3 of non-rapid eye movement sleep by 33 AE 26 min (P = 0.026), and decreased stage 1 of non-rapid eye movement sleep duration by 22 AE 17.7 min (P = 0.028), compared with sham. Slow oscillatory transcranial direct current stimulation decreased stage 1 of non-rapid eye movement sleep and wake time after sleep-onset durations, together, by 55.4 AE 51 min (P = 0.045). Slow oscillatory transcranial direct current stimulation also increased sleep efficiency by 9 AE 7% (P = 0.026), and probability of transition from stage 2 to stage 3 of non-rapid eye movement sleep by 20 AE 17.8% (P = 0.04). Meanwhile, slow oscillatory transcranial direct current stimulation decreased transitions from stage 2 of non-rapid eye movement sleep to wake by 12 AE 6.7% (P = 0.007). Our preliminary results suggest a sleep-stabilizing role for the intervention, which may mimic the effect of sleep slowwave-enhancing drugs.

Application of Transcranial Direct Current Stimulation in Neurorehabilitation: The Modulatory Effect of Sleep

“…Lastly, SWS is characterized by slow-wave oscillations (SWO), which decrease during the course of the night ( 67 ). tDCS applied during SWS reduces the decay of SWO ( 65 , 67 , 104 ), while anodal tDCS over frontocortical areas is beneficial to declarative memory when applied during SWS, an effect mediated by decreasing the rate of decrease of SWO ( 65 , 105 – 108 ). Taken together, these studies identify tDCS as a stand-alone intervention to enhance SWS and boost declarative cognitive and motor memory acquired during the day over subsequent sleep.…”

What about sleep homeostasis in insomnia? Comment on the European guideline for the diagnosis and treatment of insomnia

“…While also confirming the increased frontal power of faster EEG frequencies, we argued in a recent paper that findings of decreased slow oscillation (0.3-0.79 Hz) power proportions during SWS in insomnia patients-while SWS duration was preserved in comparison to healthy controls-could indeed also come as a support to the former evidence of homeostatic dysfunction in insomnia (Neu et al, 2015). Following these findings of lowered slow oscillation power in insomnia, a small pilot study has even reported an increase in slow oscillation power during SWS after external stimulation with slow oscillations (<0.75 Hz) by means of transcranial direct current (Saebipour et al, 2015). Conversely, these effects were related to enhanced sleep stabilization and also seemed to be associated with improvements of subjective sleep quality (Saebipour et al, 2015).…”

“…Following these findings of lowered slow oscillation power in insomnia, a small pilot study has even reported an increase in slow oscillation power during SWS after external stimulation with slow oscillations (<0.75 Hz) by means of transcranial direct current (Saebipour et al, 2015). Conversely, these effects were related to enhanced sleep stabilization and also seemed to be associated with improvements of subjective sleep quality (Saebipour et al, 2015). However, whether this increase of slow oscillations during SWS can remain stable over time, or whether daytime fatigue could improve concomitantly, remains unknown at present.…”

Alternative Strategies for Managing Insomnia: The Case of Physical Exercise and Transcranial Direct Current Stimulation. A Narrative Review

“…These results suggest that tDCS may modulate sleepiness in idiopathic patients [55][56][57]. Emerging research has demonstrated that application of slow oscillatory tDCS compared to sham-slow oscillatory tDCS decreased waking time [58][59][60]. These findings suggest a putative sleep-stabilizing role for slow oscillatory after tDCS in insomniacs [61,62].…”