SUBJECTIVE SLEEPINESS AND PHYSIOLOGICAL SLEEP TENDENCY IN HEALTHY-YOUNG MORNING AND EVENING SUBJECTS

The Multiple Sleep Latency Test (MSLT) was performed twice after 8 h a nd after 4 h of night sleep in 15 healthy young subjects (mean age: 23 y). Seven subjects could be regarded as morning, 8 subjects as evenin g types. After 8 h of sleep significantly more evening types napped at 08.00 hours and at 12.00 hours. Evening types rated themselves more s leepy on an hourly administered visual analogous scale (VAS). Sleep on set latencies (SOL) decreased, and the amount of Stages 1 and 2 increa sed in all subjects dependent on the sleep restriction condition. No s ignificant differences between morningness and eveningness concerning SOL and structure of nap structure could be observed. After 4 h of sle ep there was a marked increase in subjectively rated sleepiness during the morning hours in both groups.