Nocturnal scratching and its relationship to the disturbed sleep of itchy subjects.

This study of the relationship between nocturnal scratching and sleep is based on an analysis of 17 overnight polygraphic records of the scratch bouts and EEG of severely itchy patients. Our patients spent little time in deep orthodox sleep (stages 3 and 4), which was absent from 7 of the 17 records. Bouts of scratching were found to occur in all stages of sleep but were most numerous in stage 1 (light orthodox sleep). Sleep tended to remain stable, i.e. in a single sleep stage, for the 40 s immediately before a bout of scratching but had often changed to a more superficial stage by the time the bout had ceased, implying perhaps that scratching itself was the event linked most closely with arousal.