Linking three characteristics of insomnia: Sleep state misperception, fragmented sleep and hyperarousal

Abstract

Objectives: Insomnia seems a heterogeneous disorder with only few robust findings. There are three findings that are quite consistent across studies. First, people with insomnia overestimate the time that they spend awake during the night, a phenomenon called sleep state misperception and suggestive of ongoing mental content. Second, their sleep, especially REM sleep is frequently interrupted by arousals. Third, they experience round-the-clock hyperarousal. The present study investigated how these three characteristics may be linked. Methods: In 32 people, the reported frequency of dreams and thought-like nocturnal mentation was associated with polysomnographically assessed sleep parameters. In 1199 people, thought-like nocturnal mentation was associated with questionnaire scores on insomnia severity, hyperarousal and the speed of dissolving emotional distress. In 40 people, dreams and thought-like nocturnal mentation were measured using diaries across days of repeated assessment of distress by exposure to a negative self-conscious emotional experience of shame or embarrassment. Results: Interestingly, restless REM sleep (arousal density and eye movement density) was associated with frequently experiencing thought-like nocturnal mentation rather than dreams. Nocturnal mentation increased with the severity of insomnia, interfered with the overnight dissolving of subjective distress after a negative selfconscious emotional experience, and contributed to the severity of hyperarousal. Conclusions: The findings suggest a mechanistic link between the three most consistent characteristics of insomnia.