Abstract
Eight young adults underwent I night of auditory sleep fragmentation followed by four naps of the multiple sleep latency test and performance testing the next day. A latin-square design was used to compare results with baseline. Efforts were made to eliminate effects of learning on repeated performance tests. A mean of 303 arousals, lasting a mean of II seconds, disrupted nocturnal sleep. This sleep fragmentation was induced to mimic as closely as possible the nocturnal sleep disruption seen in subjects with upper airway resistance syndrome. There was a significant disruption of nocturnal sleep architecture with a significant overall decrease in slow-wave sleep (SWS) and a significant but more moderate decrease in rapid eye movement (REM) sleep during the fragmented night. The most interesting finding related to analysis by thirds of the night, which indicated an important increase over time in arousal threshold during SWS followed by REM sleep. This threshold increase was associated with a parallel increase in dB(A) levels needed to induce an arousal. Stages I and 2 nonrapid eye movement (NREM) sleep were less affected by the stimulation, but the amount of stage I NREM sleep decreased from the beginning to the end of the night, again indicating an increase in pressure to sleep. Following I night of sleep fragmentation, subjects had significantly shorter sleep latencies on the multiple sleep latency test for naps 2, 3 and 4. There was a significant relationship between percent nocturnal SWS and mean sleep latencies. The selected performance tests were not affected by I night of sleep fragmentation, despite the obvious sleepiness. Upper airway resistance syndrome (U ARS) has been described recently (1,2). It is seen in both genders and is associated with a complaint of daytime sleepiness and/or daytime fatigue, and an abnormal number of short electroencephalogram (EEG) arousals lasting between 2 and 14 seconds [usually not scored according to the guidelines of Rechtschaffen and Kales (3) ]. An abnormal increase in respiratory effort with mild to moderate decrease in tidal volume for one to four breaths, not translated into a drop in oxygen saturation (Sa02) measured by pulse oximetry, is also noted. Periodic leg movement syndrome, which also leads to transient EEG arousals, has been similarly reported to induce complaints of daytime sleepiness in some subjects (4) the appearance of sleepiness (5) (6) (7) has been questioned, as hypoxemia has been considered an important feature in the sleepiness observed in sleep-disordered breathing (8) . Considering the shortness of arousals associated with UARS, we questioned how much daytime sleepiness would be observed following 1 night of sleep fragmentation in a group of normal subjects with a mean age based on the last 15 patients seen and diagnosed with this syndrome in our sleep center.
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