When Does Stress End? Evidence of a Prolonged Stress Reaction in Shiftworking Truck Drivers

Abstract

This study aimed to analyze individual cortisol levels in relation to work conditions, sleep, and health parameters among truck drivers working day shifts (n = 21) compared to those working irregular shifts (n = 21). A total of 42 male truck drivers (39.8 ± 6.2 yrs) completed questionnaires about sociodemographics, job content, work environment, health, and lifestyle. Rest-activity profiles were measured using actigraphy, and cardiovascular blood parameters were collected. Salivary cortisol samples were obtained: (i) at waking time, (ii) 30 min after waking, and (iii) at bedtime, during both one workday and one day off from work. Irregular-shift workers, compared to day-shift workers, showed significantly higher waist-hip ratio, very-low-density lipoprotein (VLDL) cholesterol, tiredness after work, years working as a driver, truck vibration, and less job demand (p < .05). High cortisol levels in irregular-shift workers were correlated with certain stressors, such as short sleep duration and low job satisfaction, and to metabolic parameters, such as total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), VLDL, and triglycerides. Day-shift workers had higher cortisol levels collected 30 min after waking (p = .03) and a higher cortisol awakening response (CAR; p = .02) during workdays compared to off days. Irregular-shift workers had higher cortisol levels on their off days compared to day-shift workers (p = .03). In conclusion, for the day-shift workers, a higher cortisol response was observed on workdays compared to off days. Although no direct comparisons could be made between groups for work days, on off days the irregular-shift workers had higher cortisol levels compared to day-shift workers, suggesting a prolonged stress response in the irregular-shift group. In addition, cortisol levels were correlated with stressors and metabolic parameters. Future studies are warranted to investigate further stress responses in the context of irregular work hours. (Author correspondence: [email protected])

Keywords:

• Cortisol
• Irregular shift
• Stress
• Truck drivers

ACKNOWLEDGMENTS

We would like to acknowledge funding from the CNPq (project 474199/2008-8). M.A.U. also received support from Santander-sponsored USP—University of Surrey. T.K. is supported by the DFG (German Research Foundation), T.K. and D.J.S. are supported by the 6th Framework Project EUCLOCK (018471).

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.