Comparison of Cortisol level by Shift Cycle in Korean Firefighters

Ga-Young Lim, Tae-Won Jang, Chang-Sun Sim, Yeon Soon Ahn and Kyoung Sook Jeong
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Ga-Young Lim: Department of Public Health, Hanyang University, Seoul 04763, Korea
Tae-Won Jang: Department of Occupational and Environmental Medicine, College of Medicine, Hanynag University, Seoul 04763, Korea
Chang-Sun Sim: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Ulsan 44033, Korea
Yeon Soon Ahn: Department of Preventive Medicine, Wonju College of Medicine, Yonsei University, Wonju 26426, Korea
Kyoung Sook Jeong: Department of Occupational and Environmental Medicine, Wonju Severance Christian Hospital, Wonju 26426, Korea

IJERPH, 2020, vol. 17, issue 13, 1-14

Abstract: (1) Study Objectives: By investigating the change of cortisol levels during shift cycles among professional firefighters in Korea, this study aims to evaluate the difference between individuals’ stress response and the recovery of their circadian rhythm after working night shifts. (2) Methods: A total of 325 shift firefighters, who were working in 3, 6, 9, or 21 day cycles, participated in the study. Their urinary and serum cortisol levels were measured during the day (09–18), during the night (18–09), and every 24 h (09–09) per shift cycle, and adjustments were made for confounding factors. (3) Results: Serum cortisol levels were significantly increased after working during the night or for 24 h compared with that of working throughout the day. However, whether working night or 24 h shifts, the serum cortisol levels were undoubtedly different based on the 3, 6, 9, or 21 day cycles. In all shift cycles, the urinary cortisol level decreased during the night or throughout the 24 h shifts compared with sleeping during this time, but this was considered to be significantly applicable only to those working in 21 day cycles. Additionally, in serial measurements, the recovery of urinary cortisol secretion after a night or 24 h shift was successful for individuals working in 9 day cycles, but the recovery was delayed for those working in 6 or 21 day cycles. (4) Conclusions: After analyzing the urine cortisol levels, the study indicates that only subjects working in 9 day cycles fully recovered their circadian rhythm while those working in 6 day or 21 day cycles did not completely recover. Therefore, it is important to recognize how stressful night shifts can be, and it is crucial to enhance firefighters’ current shift cycles in order to allow sufficient recovery of their circadian rhythm as well as the prevention of disrupting their circadian rhythm after working at night. Further research is necessary to take into account the amount of work load, the challenges of being sleep deprived, and the individual’s capacity to overcome sleepiness.

Keywords: firefighter; shift cycle; shift work; cortisol; circadian rhythm (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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