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Rescheduling a three shift system at a steel rolling mill: effects of a one hour delay of shift starting times on sleep and alertness in younger and older workers.

Rosa-RR; Harma-M; Pulli-K; Mulder-M; Nasman-O
Occup Environ Med 1996 Oct; 53(10):677-685
The impact of a 1 hour delay in the start and end times of a rotating shift schedule on sleep, alertness, and performance of workers at a steel rolling mill in Finland was studied. By instituting the 1 hour delay, it was hoped that the sleep before the morning shift would be helpful in improving the alertness during the morning shift. A shift work health and safety questionnaire was used to evaluate the effects of this change. In addition to the questionnaire, recordings were made of the work/rest/sleep cycles with activity monitors worn on the wrist. Daily diaries were also kept and an on site computerized testing method of fatigue and alertness provided by the NIOSH fatigue test battery was used. The findings indicated that the delay of 1 hour in the starting time of the shift did improve sleep before the shift and improved waking fatigue, sleepiness, and performance during the morning shift. However, evening and night shift sleep and fatigue or sleepiness were negatively affected by the new change. Most workers were not satisfied with the new schedule due to social concerns. The effects did not appear to be centered on one particular age group of workers. The authors conclude that it is difficult to set optimal shift start and end times for an entire organization on a wide scale, and that tailoring shift schedules to subgroups within an organization should be attempted.
NIOSH-Author; Shift-workers; Circadian-rhythms; Sleep-disorders; Shift-work; Steel-industry; Steelworkers; Sociological-factors; Task-performance
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Occupational and Environmental Medicine