Paradoxical insomnia: The role of CAP and arousals in sleep misperception

Abstract 

Objective

The relationship between CAP parameters and subjective time perception during sleep in primary insomnia was investigated.

Patients and methods

Data collected from all-night PSG recordings of 20 patients with a diagnosis of paradoxical insomnia (misperceptors) were compared with those of 20 normal gender- and age-matched subjects (controls). Besides sleep staging, scoring measures included CAP parameters and EEG arousals.

Results

Patients and controls presented non-significant differences in the amounts of objective sleep time (464min vs. 447min) and objective sleep latency (9min vs. 8min). Compared to controls, misperceptors reported a significantly shorter time of perceived sleep (285min vs. 461min) and a significantly longer duration of perceived sleep latency (51min vs. 22min). In spite of the 11 objective awakenings, misperceptors reported only 4 subjective awakenings, while controls described 2 of the 5 objective awakenings. Arousal index (31.7/h vs. 18.6/h) and total CAP rate (58.1% vs. 35.5%) were significantly higher in misperceptors. In the sleep period between objective and subjective sleep onset, CAP rate was 64.4% in misperceptors and 45.1% in controls (p<0.002). Insomniacs showed significantly higher amounts of CAP rate in stage 1 (62.7% vs. 37.5%) and in stage 2 (53.3% vs. 33.1%), but not in slow wave sleep. CAP phase A2 subtypes were significantly increased in misperceptors (31% vs. 24%).

Conclusions

The study points out the topical role of enhanced activation and arousal instability not only in the first part of the night (mismatch between objective and subjective sleep onset) but also in the misperception of consecutive objective awakenings which are subjectively grouped together as a single prolonged event.

Keywords: Sleep, Insomnia, Cyclic alternating pattern, Arousals, Polysomnographic measures, Sleep misperception