[CAP] demonstrates increased sleep instability and correlates with fatigue and sleepiness in adults with [UARS], 2007, Guilleminault et al

[nataliezzz]

The cyclic alternating pattern demonstrates increased sleep instability and correlates with fatigue and sleepiness in adults with upper airway resistance syndrome
Christian Guilleminault, M Cecilia Lopes, Chad C Hagen, Agostinho da Rosa
https://www.researchgate.net/public..._Adults_with_Upper_Airway_Resistance_Syndrome (PDF available)

Objective: To clarify the relationship between sleep instability and subjective complaints in patients with upper airway resistance syndrome (UARS).

Methods: Thirty subjects (15 women) with UARS and 30 age- and sex-matched controls in a prospective, single-blind, case-control study. Blinded cyclic alternating pattern (CAP) electroencephalogram analysis and scales of fatigue and sleepiness were completed.

Analysis: Mann-Whitney U tests for independent, nonparametric variables between groups and chi2 tests for nonparametric variables with defined standard values.

Results: Patients with UARS had significantly more complaints of fatigue and sleepiness, compared with controls, demonstrated on their Fatigue Severity Scale (P < 0.001) and Epworth Sleepiness Scale (P < 0.001). By design, the mean apnea-hypopnea index was normal in both groups, whereas the respiratory disturbance index was greater in patients with UARS than in those without (14.5 +/- 3.0 vs 9 +/- 5.2, respectively [P < 0.001]). CAP analysis demonstrated abnormal non-rapid eye movement sleep with abnormally increased CAP rate, electroencephalogram arousals, A2 index, and A3 index. Decreased A1 index in controls was consistent with their more normal progression of sleep. CAP rate correlated with both the Epworth Sleepiness Scale (r = 0.38, P < 0.01) and the Fatigue Severity Scale (r = 0.51, P < 0.0001), and there was a positive trend between the Fatigue Severity Scale and phase A2 index (r = 0.29, P < 0.05).

Conclusion: Compared with age- and sex-matched controls, patients with UARS have higher electroencephalogram arousal indexes and important non-rapid eye movement sleep disturbances that correlate with subjective symptoms of sleepiness and fatigue. These disturbances are identifiable with sensitive measures such as CAP analysis but not with traditional diagnostic scoring systems.

 

[nataliezzz]

Re: the Epworth Sleepiness Scale, it has been shown to measure an uninterpretable mix of objective sleepiness and fatigue (which are uncorrelated symptoms in OSA patients), so the Epworth Sleepiness Scale may just be capturing fatigue (more poorly than the Fatigue Severity Scale) here.

However, it does appear that some UARS patients can be objectively sleepy (with their objective sleepiness improved by CPAP), as this was demonstrated in the first group of UARS patients identified by Dr. Guilleminault and colleagues: A cause of excessive daytime sleepiness. The upper airway resistance syndrome (1993).

The CAP framework offers a plausible mechanism for this via interference with slow-wave/deep sleep: the UARS patients in that study had a mean of 31 arousals per hour and virtually absent slow wave sleep (mean 1.2%), with CPAP restoring both slow wave sleep (to 9.7%) and MSLT (to 13.5 minutes). The 31 arousals per hour were almost certainly embedded within a much larger burden of sub-threshold CAP activity, with IFL-triggered A2 and A3 activations collectively preventing the A1-mediated EEG synchronization that normally builds and sustains slow wave sleep.

 

[nataliezzz]

Review paper on the cyclic alternating pattern:

Cyclic alternating pattern (CAP): The marker of sleep instability
Liborio Parrino, Raffaele Ferri, Oliviero Bruni, Mario G. Terzano
https://www.sciencedirect.com/science/article/abs/pii/S108707921100027X
Sci-Hub full-text link: https://sci-hub.st/10.1016/j.smrv.2011.02.003

Abstract
Cyclic alternating pattern CAP is the EEG marker of unstable sleep, a concept which is poorly appreciated among the metrics of sleep physiology. Besides, duration, depth and continuity, sleep restorative properties depend on the capacity of the brain to create periods of sustained stable sleep. This issue is not confined only to the EEG activities but reverberates upon the ongoing autonomic activity and behavioral functions, which are mutually entrained in a synchronized oscillation. CAP can be identified both in adult and children sleep and therefore represents a sensitive tool for the investigation of sleep disorders across the lifespan. The present review illustrates the story of CAP in the last 25 years, the standardized scoring criteria, the basic physiological properties and how the dimension of sleep instability has provided new insight into pathophysiology and management of sleep disorders.