Sleep architecture and rapid eye movement sleep without atonia in post-COVID-19 insomnia

Insomnia associated with COVID-19 infection is a common complaint in long-COVID. Studies to date have predominantly examined post-COVID-19 sleep disturbances with questionnaires. We aimed to investigate whether there are distinctive polysomnographic findings in post-COVID-19 insomnia compared to non-COVID-related chronic insomnia.

We included 150 patients with chronic insomnia, stratified into three groups: post-COVID-19 insomnia (N = 50), chronic insomnia during the pandemic without a history of COVID-19 infection (N = 50), and pre-pandemic chronic insomnia (N = 50). All patients underwent one-night video-polysomnography (v-PSG). The sleep architecture, respiratory variables, and rapid eye movement (REM) sleep without atonia (RWA) were compared across the groups.

Classical polysomnographic variables showed no significant differences across groups with regard to total sleep time, sleep efficiency, sleep stage percentages, and the apnea-hypopnea index. Post-COVID-19 insomnia patients had significantly increased RWA at both the chin and the flexor digitorum superficialis (p=.020 for both), and higher nocturnal heart rates (p=.046). Sleep-bout analysis indicated shorter sustained N3-sleep periods (p=.001) and longer onset to stable REM sleep (p=.016) in the post-COVID-19 insomnia group. Although sleep transitions did not withstand multiple comparison corrections, they revealed a trend toward decreased N3-sleep continuity and increased probabilities of transitioning to lighter stages (N3 → N3: unadjusted-p=.012; REM → N1: unadjusted-p=.027) in the post-COVID-19 insomnia.

Classical PSG profile of post-COVID-19 insomnia does not differ from non-COVID-related chronic insomnia. However, subtle differences in RWA and sleep integrity suggest that post-COVID-19 insomnia is driven not merely by pandemic-related stress factors but by additional physiological alterations linked to viral central nervous system involvement. Statement of Significance Insomnia is a major symptom in long-COVID, yet objective studies examining its electrophysiological underpinnings are scarce. We present the largest video-polysomnographic investigation comparing post-COVID-19 insomnia with chronic insomnia unrelated to COVID-19. While classical sleep architecture metrics did not significantly differ between post-COVID-19 insomnia and matched pre-pandemic and pandemic-era non-COVID-insomnia patients, our findings reveal subtle but important distinctions. Patients with post-COVID-19 insomnia exhibited significantly increased REM RWA, alongside trends toward altered sleep continuity, including shorter N3 sleep bouts, longer onset to stable REM sleep, and higher nocturnal heart rates. These findings suggest specific central nervous system alterations post-infection that go beyond stress-related pandemic effects and are likely linked to viral central nervous system effects. This highlights the unique neurobiological impact of COVID-19 on sleep regulation, meriting further investigation, even as established insomnia treatments remain applicable.