Comprehensive detrimental effects of a simulated frequently shifting schedule on diurnal rhythms and vigilance

ABSTRACT

Accumulating data have demonstrated that shift work causes a disturbance in circadian rhythms, which is detrimental to physiology and performance. However, the detailed effects of shift work and especially the underlying mechanisms remain to be further investigated. Frequently shifting schedules are widely used in industries, e.g., maritime tasks, oil mining, and aviation. In this work, we investigated the physiological changes and vigilance of 12 subjects who lived on a 30-day frequent shift working schedule in a confined environment, which mimics the common maritime schedules. Elevated and decreased cortisol levels were observed at different stages during the shift, suggesting the occurrence of stress and fatigue. The results of the Karolinska Sleepiness Scale (KSS) indicate increased sleepiness and a changed pattern of the rhythmicity of sleepiness during the shift. The tests of the Psychomotor Vigilance Task (PVT) reveal that the shift led to a continuously decreasing alertness as the shift working schedule progressed, which is prevalently due to the increasingly slower reaction speed. The PVT time-out errors were significantly increased in the early period but decreased in the late period. In addition, we found recoupling of the correlations between multiple physiological and cognitive variables. For instance, heartbeat rate (HR) and breath rate (BR) showed moderate correlations in the control and early periods but little in the late period. Together, these results reveal substantial alterations in diurnal rhythms, affected vigilance and changed coupling of the correlations of diurnal rhythms, physiology and cognition caused by a shift schedule. Our findings may help in the recognition of the detrimental effects of such working schedules and provide clues for the development of potential mitigations.

KEYWORDS:

• Circadian misalignment
• shift work
• vigilance
• heartbeat rate
• breath rate

Acknowledgements

We would like to thank Dr. Xin Wang and Ms. Liang Zhang (China Institute of Marine Technology & Economy, China) for their kind help in design and organization of the experiment, and we thank Prof. Fang Chen and Dr. Lu Zhang (College of Food Science and Engineering, China Agricultural University) for kindly providing the facility support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Open Fund of the National Key Laboratory of Human Factors Engineering in the Astronaut Center of China [SYFD180051809K], the National Natural Science Foundation of China [31571205 and 31871188], the Qian Xuesen Space Exploration Experimental Cultivation Project. [TKTSPY-2020-04-01] and the Lingang Laboratory & National Key Laboratory of Human Factors Engineering Joint Grant.