Awakening thresholds and (REM) sleep perception in insomnia patients and good sleepers controls

Introduction: Insomnia disorder (ID) is a frequent sleep disorder coupled with increased risks for somatic and mental illness. While subjective complaints are severe, polysomnography (PSG) parameters show only modest differences between groups. In previous studies we have postulated that REM (rapid eye movement) sleep may be especially vulnerable to be perceived as wake. To assess this issue more directly, we determined auditory waking thresholds and sleep perception in ID patients and healthy control subjects (GSC) in N2 and REM sleep. Materials and Methods: Twenty‐seven ID patients and 27 ageand gender‐ matched controls were included. Four consecutive nights were assessed in the sleep laboratory, with nights 3 and 4 each containing three awakenings either from stable N2 or REM sleep. Results: With subjective sleep of course strongly impaired, PSG data of the 1st and 2nd night showed the commonly observed relatively weak group differences. Awakening thresholds in ID patients did not differ from GSC, but decreased over the course of the night. ID patients indicated significantly more frequently than GSC having been awake when woken from REM sleep but not from N2 and were less sure when indicating they had been asleep. Additionally, ID subjects rated their REM sleep mentation as more emotionally negative compared to GSC. Conclusions: This study presents direct evidence that the subjective experience of insomnia might be specifically coupled to the REM sleep state. Assuming chronic hyperarousal as a central pathophysiologically relevant pathway for insomnia, this might become especially evident during REM sleep, thus reflecting a “hybrid” sleep state in insomnia being coupled with altered sleep perception. Disclosure: The study was funded by the DFG (Deutsche Forschungsgemeinschaft; RI 565/13–1).