On the potential clinical relevance of the length of arousals from sleep in patients with obstructive sleep apnea.

STUDY OBJECTIVES: To assess, in individuals referred for evaluation of obstructive sleep apnea, the potential clinical significance of brief versus longer arousals from sleep. METHODS: Full-night polysomnographic tracings from 100 patients referred for evaluation of obstructive sleep apnea were analyzed to delineate the duration of each arousal event. These data were then correlated to the patient's subjective perception of sleepiness as estimated by the Epworth Sleepiness Scale (ESS). RESULTS: A significant relationship (p < .0001, r(2) = .167) was noted between the frequency of the longer arousals (> 15 seconds) and the ESS. This relationship was significant, but distinctly weaker (p = .004, r(2) = .073), with the shorter arousals (3-15 seconds); moreover, the association with the brief arousals failed to remain significant (p = .678) after controlling for the effect of the longer arousals. CONCLUSIONS: Individuals with obstructive sleep apnea experience frequent respiratory event associated cortical arousals, many of which are greater than 15 seconds in duration. These longer arousals, which, in this study, constituted 18.4% of all arousals and accounted for 37.5% of the total arousal time, correlate more closely with the ESS than does the frequency or time attributable to the more numerous brief arousals. This suggests that these more-prolonged arousal events may have a greater impact on the restorative aspect of sleep, or on the perception thereof.

On a characteristic of cortical arousals in individuals with obstructive sleep apnea.

STUDY OBJECTIVE: To identify the frequency and duration of those arousals exceeding fifteen seconds in length, in patients with obstructive sleep apnea. METHODS: The polysomnographic tracings from fifty consecutive patients with obstructive sleep apnea were carefully analyzed to delineate the duration of each arousal event. These data were then collated to define the frequency of arousals of differing durations, and the impact thereof on the total time spent in an arousal state. RESULTS: Respiratory event related prolonged arousals (> or = 15 seconds) were identified in 100% of the patients. These longer arousals accounted for 22% of all arousals, and 37% of all arousal time. The frequency of the arousals decreased with CPAP treatment, as did the time spent in an arousal state. CONCLUSIONS: Patients with obstructive sleep apnea experience frequent respiratory event associated cortical arousals, many of which are greater than fifteen seconds in duration. There is the potential for these more prolonged arousals to be scored as epochs of Wake, which may result in their being reported as contributing to Wake After Sleep Onset (WASO) time, rather than as distinct arousals. This may result in an under-appreciation of both the frequency with which these prolonged arousals may occur, and the potential effect these arousals may have on the severity of the sleep fragmentation.