If awakened from stage Delta sleep the physician will find that they can not think clearly, talk readily and experience retrograde amnesia. The human body tends to respond to sleep deprivation by acquiring rebound sleep of the type of sleep that it was most deprived. In other words if you were on call and napping for approximately 60-80 minutes you may find that you were being selectively deprived of stage REM sleep. And this is the stage of sleep your body will seek most when rebound sleep occurs. We respond most poorly when we are aroused from stage delta sleep.
Delta sleep is the stage of sleep where our bodies obtain the most physical restorative effect.
It is also the easiest stage of sleep to eliminate from our nights effort. Research and clinical experience has shown that patients with some types of sleep disorders such as obstructive sleep apnea and periodic limb movement syndrome will report excessive daytime sleepiness. When studied they are found to have no stage Delta sleep. Should the physician find themselves the victims of chronic sleep restriction or frequent nocturnal awakenings they could develop symptoms similar to narcolepsy. They may experience premature REM sleep, hypnaggogic hallucinations, sleep paralysis or an increase in hypnic myoclonia and have no pathology other than sleep deprivation.