Transcranial photobiomodulation improves sleep quality, reduces daytime sleepiness, and modulates delta power in chronic insomnia: a randomized controlled trial

Abstract

Chronic insomnia is a prevalent disorder with significant health consequences and limitations in current treatments. This randomized controlled trial evaluated the efficacy of transcranial photobiomodulation (tPBM) on subjective sleep quality, daytime sleepiness, and quantitative EEG biomarkers in chronic insomnia. Thirty adults with chronic insomnia (DSM-5 criteria) were randomized to receive active tPBM (n = 15) or sham treatment (n = 15). Active tPBM (810 nm wavelength; 250mW/cm² irradiance; 60 J/cm² energy density) was applied to frontal cortical regions for 10 min per session over 3 consecutive days. Primary outcomes were Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and absolute delta power (1-4 Hz) at frontal EEG sites, assessed at baseline and 1-week post-treatment. Significant improvements were observed in the tPBM group compared to sham: PSQI global score (mean difference: -4.6 points; 95% CI: -7.2 to -2.0; p = 0.004, η²=0.272), ESS total score (mean difference: -4.1 points; 95% CI: -6.8 to -1.4; p = 0.015, η²=0.209), and absolute delta power at multiple frontal sites (e.g., Fp1: p = 0.001, η²=0.418; Fz: p < 0.001, η²=0.450). No serious adverse events occurred. Three sessions of frontal tPBM (810 nm, 60 J/cm²) significantly improved subjective sleep quality, reduced daytime sleepiness, and normalized pathological wake frontal delta activity in chronic insomnia. These findings support tPBM as a promising, safe neuromodulatory intervention targeting thalamocortical dysrhythmia. Larger trials with longer follow-up are warranted.

Keywords: Delta waves; Electroencephalography; Insomnia; Low-level laser therapy; Photobiomodulation; Sleep quality.