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.