A randomized controlled trial of alpha phase-locked auditory stimulation to treat symptoms of sleep onset insomnia
Scientific Reports volume 14, Article number: 13039 (2024 ) Cite this article
Sleep onset insomnia is a pervasive problem that contributes significantly to the poor health outcomes associated with insufficient sleep. Auditory stimuli phase-locked to slow-wave sleep oscillations have been shown to augment deep sleep, but it is unknown whether a similar approach can be used to accelerate sleep onset. The present randomized controlled crossover trial enrolled adults with objectively verified sleep onset latencies (SOLs) greater than 30 min to test the effect of auditory stimuli delivered at specific phases of participants’ alpha oscillations prior to sleep onset. During the intervention week, participants wore an electroencephalogram (EEG)-enabled headband that delivered acoustic pulses timed to arrive anti-phase with alpha for 30 min (Stimulation). During the Sham week, the headband silently recorded EEG. The primary outcome was SOL determined by blinded scoring of EEG records. For the 21 subjects included in the analyses, stimulation had a significant effect on SOL according to a linear mixed effects model (p = 0.0019), and weekly average SOL decreased by 10.5 ± 15.9 min (29.3 ± 44.4%). These data suggest that phase-locked acoustic stimulation can be a viable alternative to pharmaceuticals to accelerate sleep onset in individuals with prolonged sleep onset latencies. Trial Registration: This trial was first registered on clinicaltrials.gov on 24/02/2023 under the name Sounds Locked to ElectroEncephalogram Phase For the Acceleration of Sleep Onset Time (SLEEPFAST), and assigned registry number NCT05743114.
Insufficient sleep is a global problem that is associated with an increased risk of premature mortality and a long list of adverse health conditions1. Insomnia is the most prevalent sleep disorder among adults, and more than 60% of individuals experiencing insomnia report difficulties initiating sleep2. Many pharmaceutical treatments are available to treat insomnia. However, a recent meta-analysis found that many effective treatments were poorly tolerated, while well-tolerated drugs lacked evidence supporting their efficacy3. Recently, there has been growing interest in acoustic neuromodulation as an alternative to sleep medications for improving sleep quality. This approach uses sound pulses phase-locked to neural oscillations measured in real-time via electroencephalogram (EEG). Studies have shown this method to have health benefits when applied to slow (0.5–1.5 Hz) oscillations present during non-rapid eye movement (NREM) stage 3 (“deep”) sleep, including enhanced memory consolidation4,5,6; immune function7; and autonomic balance8. However, stimulation at slow-wave frequencies outside of N3 sleep has not been shown to improve sleep onset and in fact may delay the initiation of sleep9. It remains unknown whether phase-locked acoustic stimulation can be used to address symptoms of insomnia.
