A controlled intervention study on the effects of a very rapidly forward rotating shift system on sleep-wakefulness and well-being among young and elderly shift workers.

Shift work is related to problems in sleep/wakefulness and social life. The effects of a very rapidly forward rotating shift system on sleep, health and well-being of young (-45) and elderly (45+) maintenance workers were studied by a controlled intervention study. In the beginning, all the workers had a continuous backward rotating three-shift system. A very quickly forward rotating shift system was developed, avoiding consecutive night shifts and with more free-time between the individual shifts. The effect of the new shift system on sleep/wakefulness and general well-being was studied by questionnaire and field studies including on-site registration of sleep (actigraphy), subjective sleepiness (KSS) and psychomotor performance (PVT). Based on a linear mixed model for repeated measurements, the new shift system increased the main sleep length after the night shift and improved alertness and PVT performance during the night shift among the older workers. Alertness also improved during free-time after the night shift and sleep complaints decreased after all shifts. The workers on the new shift schedule perceived the effects of the new shift system on sleep, alertness, general health, well-being at work, social and family life more positively than the workers in the old shift system. At the end of the study, all subjects voted for the new shift system. It is concluded that although the new shift system increased the operating hours at night, the very rapidly forward rotating shift system had positive effects on the sleep, alertness and well-being of especially the older shift workers.