Higher levels of nocturnal cognitive arousal are associated with objective sleep disturbance in both individuals with and without insomnia; the most frequent parameter associated with nocturnal cognitive arousal was difficulty falling asleep, according to an article published in Sleep Medicine.

Forms of cognitive arousal include rumination and worry before bedtime and have been implicated in the etiology of sleep disturbances. Cognitive arousal has also been linked to an elevated risk for insomnia comorbidities such as anxiety, depression, and cardiovascular disease. Researchers sought to explore the associations of cognitive arousal with objective nocturnal wakefulness and indicators of physiologic hyperarousal in both healthy sleepers and those with insomnia.

A total of 52 adults (51.9% women) were included in the study; 18 of these had insomnia and 34 were healthy sleepers. Participants’ ages ranged from 18 to 51 years; the majority of the participants were non-Hispanic White (61.5%) or non-Hispanic Black (23.1%).

Participants underwent 2 overnight polysomonography (PSG) studies; the first night (adaption night) detected disorders other than insomnia (apnea, hypopnea) and the second was considered the baseline night. PSG sleep parameters/nocturnal wakefulness and somatic arousal were recorded for each night. After the baseline night, participants underwent 4 daytime naps that included multiple sleep latency tests (MSLTs).


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Additional baseline measures included DSM-IV Insomnia Disorder diagnosis, self-reported sleep parameters (habitual sleep latency, nighttime awakenings, wake after sleep onset, and total sleep time), insomnia severity, and global sleep quality. Depressive symptoms were measured by the Patient Health Questionnaire (PHQ-9), which was administered to all patients in the trial.

Patients with insomnia disorder reported higher levels of nocturnal cognitive arousal while trying to fall asleep on the adaptation night and baseline night compared to healthy sleepers. No significant differences were found in sleep latency, wake after sleep onset, sleep efficiency, or total sleep time for the full sample on the adaptation night. On the baseline night, the only group difference identified was objective sleep disturbance scores ranking higher among insomnia participants compared with healthy sleepers.

On the adaptation night, nocturnal cognitive arousal was associated with longer sleep latency, longer wake after sleep onset, and lower sleep efficacy. On the baseline night, nocturnal cognitive arousal was associated with longer sleep latency, and lower sleep efficacy, but no significant differences were found for wake after sleep onset. 

In an analysis of PSG scores, participants with high nocturnal cognitive arousal (n=9) took 37 minutes longer to fall asleep and 45 minutes longer to reach persistent sleep than those with low cognitive arousal (n=43). Similarly, participants with high cognitive arousal spent 44 more minutes awake after initial sleep onset than those with low cognitive arousal. “In accordance with these differences in sleep latency and wake after sleep onset, we observed large differences in sleep efficiency (86.97% vs 71.06%) and total sleep time (6.95 vs 5.70 h),” the researchers reported. Insomnia diagnosis, depression, and somatic arousal were not associated with any of the PSG sleep parameters or MSLT latency.  

“A critical finding from our study is that nocturnal cognitive arousal was more robustly associated with nocturnal wake and indicators of hyperarousal than insomnia diagnosis, depressive symptoms, or even self-reported presleep somatic arousal,” concluded the authors. “As insomnia patients endorse high levels of cognitive arousal, our data suggest that ruminative thinking could potentially be an important active ingredient in insomnia with regard to objective sleep disturbance and 24-[hour] hyperarousal.”

Reference

Kalmbach DA, Buysse DJ, Cheng P, Roth T, Yang A, Drake CL. Nocturnal cognitive arousal is associated with objective sleep disturbance and indicators of physiologic hyperarousal in good sleepers and individuals with insomnia disorder. Sleep Med. 2020;71:151-160.