Restless REM sleep may interfere with the overnight resolution of emotional distress, which in turn may promote the development of chronic hyperarousal, according to research published online ahead of print February 8 in Proceedings of the National Academy of Sciences. These findings suggest that REM sleep's role in regulating emotions is clinically relevant in insomnia and other disorders.
Prior research has identified hyperarousal as a key factor in the cause of chronic insomnia, but the mechanisms underlying hyperarousal are not well understood. "Given the role of REM sleep in emotion regulation, we hypothesized that restless REM sleep could interfere with the overnight resolution of emotional distress, thus contributing to accumulation of arousal," said Rick Wassing, MSc, a doctoral student at the Netherlands Institute for Neuroscience in Amsterdam, and colleagues.
To test their hypothesis, the investigators had 1,199 participants in the Netherlands Sleep Registry complete online questionnaires on insomnia severity, hyperarousal, self-conscious emotional distress, and thoughtlike rather than dreamlike nocturnal mentation. The investigators had assessed 32 people with polysomnography to validate thoughtlike nocturnal mentation as a specific proxy for restless REM sleep (ie, REM sleep with a high number of phasic events, including arousals and eye movements). Participants had an average age of 52.1, and approximately 74% of participants were female.
Using multiple regression analyses and structural equation modeling, the investigators found that insomnia severity was associated with how often emotional distress lasted overnight, but not with how often distress resolved within a day. Insomnia severity also was associated with nocturnal mentation and hyperarousal.
Distress that lasted overnight was associated with higher hyperarousal ratings, whereas short-lasting distress was not associated with hyperarousal. Adjusting for major life events and the possible presence of other disorders only had a marginal effect on the results.
"Most importantly, the present findings show that the overnight resolution of distress from shame is compromised in people with insomnia; that this deficit contributes to hyperarousal; and that this deficit seems, in part, to be due to a process that is reflected in a high density of arousals and eye movements in REM sleep and concomitant thoughtlike nocturnal mentation," the investigators said.
—Jake Remaly
