Comparison of Cortisol level by Shift Cycle in Korean Firefighters

Abstract

<jats:p>(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.</jats:p>

Relationships among shift work, hair cortisol concentration and sleep disorders: a cross-sectional study in China

“…Previous study in Korean firefighters indicated that the serum cortisol response was positively related to nightshift work and serum cortisol levels were different by shift schedule. 22 In our study, shift workers had higher HCC level compared with day workers, and the differences between different shift patterns were not statistically significant. The reason for the inconsistent results may be that serum cortisol fluctuates according to the circadian rhythm and is easily disturbed by external factors, while HCC is stable and can reflect the long-term cortisol exposure of body.…”

The Development of a Sleep Intervention for Firefighters: The FIT-IN (Firefighter’s Therapy for Insomnia and Nightmares) Study

“…This study was conducted as part of the sleep panel study (SLEPS) to improve sleep disturbance in Korean firefighters [ 36 , 37 ]. This study was conducted as part of a larger 7-year sleep panel study (SLEPS) to improve sleep disturbance in Korean firefighters [ 36 , 37 ]. The purpose of SLEPS was to investigate sleep disturbance among Korean firefighters and develop and investigate the efficacy of a sleep intervention program, with the final goal of nationwide dissemination.…”

Investigating the influence of shift work rosters on stress measured as cortisol in hair during the SARS-CoV-2 pandemic

“…A follow-up study of Slovenian nurses showed lower HCC during the more severe COVID-19 wave in fall 2021 with more COVID-19 cases and deaths compared to spring 2021, which could be explained by the novelty and uncertainty in the early phase of the pandemic in spring ( Rajcani et al, 2021a ). Further research is needed regarding to clarify the effects of perceived stress, work-related stressors, and pandemic-related long-term stress on HCC in non-healthcare shift workers, A comparison between shift workers with and without night shifts would also be desirable, as there is evidence that cortisol concentrations are elevated after night shifts ( Lim et al, 2020 , Zhang et al, 2020 ).…”