Are there permanent effects of night shift work on sleep?

The sleep structures, patterns and subjective evaluations of 50-60 year old nurses with varying amounts of night shift experience during their nursing careers were compared with the sleep of 50-60 year old females without night shift experience. Seven nurses had extensive prior night shift experience and were currently on night shift schedules, seven nurses had extensive night shift experience but were on current day schedules, five nurses, currently on day schedules, had had limited night shift experience. There were limited differences between the nurses on current day schedules and the non shift women. The current night shift scheduled nurses showed characteristic displaced sleep responses. It was concluded that there is little support for an hypothesis of a permanent effect of night shift work experience on subsequent sleep.