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Updated: Aug 9, 2026

Collecting Sleep, Circadian, Fatigue, and Performance Data in Complex Operational Environments
Published on: August 8, 2019
Circadian adjustment and stress in operators under fast rotating 12-hour shifts
1Department of Physiology, Psychology and Ergonomics, National Center of Hygiene, Medical Ecology and Nutrition, 15 Dimiter Nestorov Boul., 1431 Sofia, Bulgaria.
Abstract:
The aim of the investigation was to follow the time-of-day variations of some circadian and stress indicators during fast rotating 12-hour shifts. The study covered twenty-one male operators in thermoelectric power plant aged 35.7 +/- 8.5 years. The time-of-day variations of 6-sulphathoxymelatonin (aMT6s), the main melatonin metabolite, 11-oxycorticosteroids (11-OCS), catecholamines and oral temperature were followed during the 2nd day shift and two consecutive night shifts. The aMT6s was determined by RIA and the 11-OCS and catecholamines by fluoriphotometric methods. Moderate general activation and daily oriented circadian rhythms of aMT6s, 11-OCS and oral temperature were found in the investigated operators. The night shiftwork showed significant impact on melatonin peak values at fast rotating 12-hour shiftwork.
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