Insomnia is a highly prevalent sleep disorder affecting up to 35% of the general population – and can significantly impair quality of life.
Researchers have been investigating new non-pharmacological treatment options like transcranial electric stimulation (TES) and repetitive transcranial magnetic stimulation (rTMS) to treat insomnia symptoms.
A new meta-analysis published in Frontiers in Psychiatry reviewed the evidence from randomized controlled trials on the effectiveness of TES and rTMS for insomnia treatment.
The analysis found that both techniques show potential for improving sleep quality, with rTMS demonstrating larger effects.
Some key takeaways:
- TES was superior to sham controls in improving subjective sleep quality on the Pittsburgh Sleep Quality Index (PSQI), but not on objective sleep measures like polysomnography.
- rTMS outperformed sham controls on both subjective PSQI scores and objective sleep parameters including sleep efficiency, sleep onset latency, total sleep time and wake after sleep onset.
- The effects of rTMS on sleep quality were maintained 1-4 weeks after treatment completion.
- Stimulation parameters like number of sessions and pulses modulated rTMS effects, suggesting optimal protocols still need refinement.
- Males may respond better to rTMS than females for insomnia treatment.
- Both techniques had mild side effects like discomfort, but were well-tolerated overall.
Source: Front Psychiatry 2021
This meta-analysis helps strengthen the evidence base for using non-invasive brain stimulation as an insomnia treatment approach.
Overview of Transcranial Brain Stimulation Techniques
TES and rTMS are two forms of non-invasive brain stimulation (NIBS) increasingly studied for insomnia relief.
TES techniques like transcranial direct current stimulation (tDCS) involve applying a weak electrical current to the scalp to modulate brain activity.
rTMS uses electromagnetic coils placed over the scalp to stimulate brain regions with magnetic pulses.
Both approaches are relatively safe, painless and well-tolerated.
However, they differ in their mechanisms of action and stimulation focality.
TES has poor spatial targeting but is portable and suitable for at-home use.
rTMS allows targeted stimulation of deep brain structures but requires in-clinic administration.
Prior reviews summarized the promise of NIBS for insomnia but without meta-analysis.
This new review aimed to statistically synthesize all randomized sham-controlled trial findings on TES and rTMS for insomnia treatment.
It also examined the impact of moderating factors like stimulation parameters.
The Analysis Included 16 TES Trials and 27 rTMS Trials for Insomnia
The researchers systematically searched medical databases for all randomized sham-controlled trials testing TES or rTMS for insomnia.
16 TES studies (8 cranial electrotherapy stimulation, 7 tDCS, 1 tACS) and 27 rTMS studies were identified for inclusion.
The studies covered ~1300 insomnia patients combined.
The mean age was 50 years, and there were more female than male participants.
The trials applied stimulation for 2-4 weeks on average and assessed sleep subjectively (commonly with the PSQI questionnaire) and/or objectively (like with polysomnography).
Meta-Analysis Findings on TES and rTMS Effects for Sleep & Insomnia
The meta-analysis statistically pooled results across the included studies to derive overall effects on sleep outcomes.
The key effects found were:
TES
- TES was superior to sham on the PSQI sleep quality score immediately post-treatment. The average improvement was a 1.17 point greater reduction on the PSQI compared to sham.
- However, TES was not significantly better than sham on objective polysomnography sleep measures like sleep efficiency, onset latency and total sleep time.
- Analysis of moderating factors did not reveal significant impacts of TES stimulation parameters or participant factors on treatment efficacy. But the small number of studies limited detection of subtle effects.
rTMS
- rTMS significantly outperformed sham on both the PSQI subjective sleep quality score and objective polysomnography measures of sleep efficiency, total sleep time, onset latency and wake after sleep onset.
- The benefits of rTMS over sham on the PSQI score remained significant at 1-4 weeks post-treatment follow-up.
- The number of rTMS sessions and pulses per session positively impacted treatment effects on sleep efficiency and PSQI scores.
- Shorter single session duration improved total sleep time and PSQI outcomes.
- Male gender also enhanced rTMS effects on the PSQI sleep quality score.
In summary, while both TES and rTMS demonstrate potential for improving insomnia severity, rTMS shows larger effects on both subjective and objective sleep outcomes.
rTMS benefits also appear more sustained over at least 1 month follow-up.
Optimization of rTMS protocols accounting for moderating factors could further enhance efficacy.
Possible Reasons for Superior Efficacy of rTMS Over TES in Insomnia
The meta-analysis results suggest rTMS is more effective than TES for combating insomnia overall.
There are several potential explanations the researchers propose:
- Clinical heterogeneity – the small number of TES trials limited conclusions about comparative efficacy. More TES studies could change results.
- Stimulation mechanisms – the magnetic pulses of rTMS can directly reach and stimulate deep cortical brain regions. The weak electrical currents of TES have more limited ability to penetrate the scalp and influence deeper structures.
- Stimulation focality – rTMS allows targeting specific brain regions like the dorsolateral prefrontal cortex, while TES has poor spatial specificity. Focused stimulation of regions implicated in insomnia may underlie rTMS benefits.
In summary, the more powerful and targeted neuromodulation of rTMS could be superior for manipulating brain activity patterns underlying insomnia.
But more research directly comparing approaches is still needed.
Dose-Dependent Effects: Optimizing rTMS Protocols for Sleep
Since rTMS demonstrated larger effects than TES overall, the researchers examined how moderating factors impacted rTMS treatment efficacy.
The goal was to glean insights into optimal stimulation protocols.
The main findings were:
- More treatment sessions enhanced the benefits of rTMS for sleep efficiency and sleep quality.
- Applying more magnetic pulses per session also amplified improvements in overall sleep quality.
- Shorter single session duration improved sleep time and quality. Prolonged stimulation may reverse effects.
- Male gender predicted enhanced rTMS effects on sleep quality score.
These results suggest potential dose-dependent and individual factors that can be optimized to boost rTMS efficacy for insomnia.
However, more research is still needed to replicate the effects and elaborate underlying mechanisms.
Future studies should also examine long-term follow-up since the current analysis was limited to 1 month post-treatment.
Sustained impacts on sleep weeks to months after rTMS cessation would strengthen the viability of this approach.
Both TES and rTMS are Safe Options for Insomnia Treatment
Importantly, the meta-analysis found both TES and rTMS have mild side effect profiles overall.
The most common adverse effects were minor discomfort, headache, dizziness or pain at the stimulation site.
There were no serious safety issues reported.
These findings add to the evidence base supporting non-invasive brain stimulation as a well-tolerated insomnia treatment method.
However, the researchers highlight several limitations of the analysis to keep in mind:
- Methodological quality of included studies was moderate and lacked details on randomization processes.
- There was heterogeneity between trials in participant characteristics, insomnia diagnosis methods and stimulation parameters.
- The small number of available trials limits generalizability of results.
- Longer-term follow-up was lacking to determine if effects are sustained.
Nevertheless, this rigorous meta-analysis makes an important contribution by statistically synthesizing sham-controlled evidence on TES and rTMS for insomnia across dozens of trials and hundreds of patients.
Cautious Optimism: Non-Invasive Brain Stimulation Approaches for Insomnia
In conclusion, this meta-analysis adds to the growing research base supporting transcranial brain stimulation techniques as promising insomnia treatment approaches.
rTMS demonstrates larger effects than TES overall, but both modalities show potential for improving sleep difficulties.
The researchers note cautious optimism is warranted along with further research to replicate and extend the findings.
If results hold, non-invasive brain stimulation could provide a novel therapeutic tool for managing insomnia and its detrimental impacts on mental and physical well-being.
References
- Study: Effectiveness of TES and rTMS for the treatment of insomnia: meta-analysis and meta-regression of randomized sham-controlled trials
- Authors: Haixia Ma et al. (2021)
