Background: Despite numerous studies on auditory event-related potentials (ERPs) in insomnia disorder (ID), the results are inconsistent across different ERP components (e.g. N1, P2, P3, and N350), types of auditory stimuli (e.g. standard and deviant), and stages of sleep (e.g. wakefulness, NREM sleep, and REM sleep). In light of this variability, we conducted a systematic meta-analysis of previous auditory ERP studies in ID to provide a quantitative review of the existing literature.
Methods: Relevant literatures were searched on the Embase, PubMed/MEDLINE, PsycINFO and Cochrane Library. A total of 12 studies comprising 497 participants were finally included in this meta-analysis. The study protocol was registered with PROSPERO under the registration number CRD42022308348.
Results: We found that patients with ID have significantly decreased N1 (Hedges' g = 0.34, 95%CI [0.04, 0.65]) and P3 (Hedges'g = -1.21, 95%CI [-2.37, -0.06]) amplitudes during wakefulness. In addition, decreases in P2 (Hedges'g = -0.57, 95%CI [-0.96, -0.17]) amplitude during wakefulness and N350 (Hedges' g = 0.73, 95%CI [0.36, 1.09]) amplitude during NREM.
Conclusions: This meta-analysis represents the first systematic investigation of ERP features across different stages of sleep in individuals with ID. Our results suggest that in patients with insomnia, the absence or deficiency of arousal inhibition during the nighttime sleep initiation or maintenance process may interfere with the normal process of sleep.