Arousal components which differentiate the MWT from the MSLT

Study Objectives: The purpose of this study was to determine the relative c ontribution of the instruction to maintain wakefulness versus posture chang e as major components determining sleep latency in the MWT as compared to t he MSLT. Design and Setting: After adaptation. subjects spent 3 nights and the follo wing days in the laboratory. On each day, Ss had eight sleep latency measur ements including four sleep latency tests from two of the following conditi ons: Lay down and Sleep (MSLT); Lay down and stay Awake; Sit up and Sleep; Sit up and stay Awake (MWT); and sit in a chair in front of a Computer and stay awake. Participants: Participants were 14 young adult normal sleepers. Interventions: NA Measurement and Results: Significant differences in sleep latency were foun d for each condition with respect to all of the others except that the Comp uter condition did not differ from the Sit-Awake condition. Means for condi tions were: Lay-Sleep - 11.1 minutes; Sit-Sleep - 17.7 minutes; Lay-Awake - 21.7 minutes; Sit-Awake - 29.0 minutes; Computer - 30.1 minutes. Correlati ons between conditions declined as subjects sat up. Conclusions: The MWT differs from the MSLT by taking advantage of the arous al system (motivation and posture) to maintain alertness (i.e., increase sl eep latency). These arousal effects are additive. MSLT results may not alwa ys correlate well with MWT results because the MWT measures the combined ef fects of the sleep and arousal systems while the MSLT, in ideal situations, measures only sleepiness.