Vigilance stages and performance in OSAS patients in a monotonous reactiontime task

Objectives: To develop improved methods for objective assessment of daytime vigilance. This is important in the diagnosis and therapy control of sleep disorders associated with excessive daytime sleepiness (EDS). Methods: Twenty-one patients with EDS due to obstructive sleep apnea were r ecorded during a daytime 90 min reaction time (RT) test in a monotonous sit uation. Two EEG, two EOG and a submental EMG channel were recorded simultan eously. The recordings were divided into short, stationary segments of vari able length (0.5-2 s) and classified into 7 stages using our previously des cribed system, which includes additional stages for drowsiness. Results: The duration of RT was linearly correlated to the vigilance state (P < 0.05). The appearance of slow eye movements (SEM) was more consistentl y related to performance impairment than EEG changes. Conclusions: Our system can provide a better tracking of vigilance changes than the standardized sleep stage scoring. A 1-2 h test is useful in the as sessment of the performance of a subject suffering from EDS. We found that SEMs indicate more sensitive and consistent EDS-related performance impairm ent than changes in EEG activity. (C) 2000 Elsevier Science Ireland Ltd. Al l rights reserved.