Poor recovery sleep after sleep deprivation in delayed sleep phase syndrome

To clarify disturbances in sleep regulation in patients with delayed sleep phase syndrome (DSPS), we studied three patients with DSPS and seven health y controls. Sleep propensity and melatonin rhythms after 24-h sleep depriva tion were investigated under dim light condition by using the ultra-short s leep-wake schedule. The sleep propensity curves displayed clear differences between DSPS patients and the controls. During the subjective day when mel atonin was not produced, recovery sleep after the sleep deprivation did not occur in DSPS patients, while recovery sleep occurred during the subjectiv e day in controls, This: suggests that DSPS may involve problems related to the homeostatic regulation of sleep after sleep deprivation.