EEG correlates of sleep stages, sleep discrepancy, and insomnia: a comparative analysis of people with insomnia and healthy sleepers using spectral power and sample entropy.

This study investigated neurophysiological differences between individuals with and without insomnia across sleep stages and sleep discrepancy conditions using electroencephalography (EEG). EEG band powers (Delta, Beta) and entropy metrics (Sample Entropy and Multiscale Sample Entropy) were analyzed from each epoch of overnight polysomnography in 64 participants. Linear mixed-effects modeling was used to examine the influence of insomnia status, sleep stage, and electrode location on these EEG metrics. Results indicated that the EEG metrics were strongly correlated with physiological sleep stages but did not effectively distinguish self-reported sleep perception within the same polysomnographic sleep stage. Additionally, these metrics did not consistently differentiate individuals with insomnia from good sleeper controls across all conditions. Rather, individuals with insomnia exhibited regional patterns of Delta power during wakefulness, increased sample entropy during REM sleep, and decreased Beta power during positive discrepancy. These findings highlight physiological features associated with sleep stages, insomnia, and sleep discrepancy while emphasizing their complexity and the limitations of standard EEG metrics alone. Future work integrating physiological measures with self-report data may provide enhanced characterization of insomnia-related neurophysiological changes.