Facility-Measured Sleep Electroencephalographic Microstructures in Long COVID.

Observed Findings

• Long COVID participants showed elevated slow-oscillation power during wake-before-sleep and REM sleep, compared to healthy controls.
• Long COVID participants displayed faster within-spindle frequency decline (chirp) and shorter slow-oscillation peak duration in frontal regions during N2 and N3 sleep.
• Long COVID showed widespread, early spindle–slow-oscillation coupling at the trough of slow oscillations, with early fast spindle–slow-oscillation coupling associated with worse self-reported sleep quality.
• ME/CFS participants shared some alterations with long COVID but additionally exhibited elevated slow-spindle densities (uncoupled to slow oscillations), increased alpha-delta patterns in the first sleep half, and widespread elevated infraslow oscillation power in the slow sigma band (11–13 Hz).

Inferred Conclusions

• The authors interpret the observed EEG microstructure changes as "plausibly pathological," suggesting that post-infectious processes (long COVID and ME/CFS) are associated with distinct alterations in sleep neurophysiology that may underlie unrefreshing sleep and fatigue.
• The divergent EEG signatures between long COVID and ME/CFS (e.g., spindle–slow-oscillation coupling vs. elevated infraslow power) suggest potentially different neurobiological sleep disturbances across post-infectious syndromes, though direct within-study comparison was limited.
• The authors propose that sleep EEG microstructure offers a "window" into the pathobiology of post-infectious fatigue, implying future research might use these measures as biomarkers or mechanistic probes.

Remaining Questions