Shift work parameters and disruption of diurnal cortisol production in female hospital employees

ABSTRACT

Shift work is associated with an increased risk of cardiovascular diseases (CVD). Disruption of cortisol production is a potential underlying mechanism. This study explored the associations of diurnal quantity and pattern of cortisol production in relation to (1) current shift work status (exclusive day versus rotating days and nights), (2) years of past shift work and (3) parameters of rotating shift work (timing, length and intensity). Female hospital employees (160 day workers and 168 rotating shift workers) from southeastern Ontario, Canada, participated in a cross-sectional study. Participants completed a baseline questionnaire and measures of body height, weight, and waist circumference were taken. Midstream urine samples were collected over two separate 24-hour periods to measure creatinine-adjusted cortisol. Total diurnal cortisol production and pattern were described with two measures of the area under the curve. The effect of shift work on cortisol was modeled using multivariable linear regression analyses. Cortisol production in day workers and shift workers on their day shift were similar; however, shift workers on the night shift had flatter diurnal cortisol curves and produced less cortisol. This suggests that night work is associated with an acute attenuation of cortisol production.

KEYWORDS:

• cortisol
• shift work
• shift work parameters

Acknowledgments

We thank other members of the investigative team: Christine Collier, Ian Janssen and Linda McGillis Hall. We would also like to thank study participants, and research staff. This work was completed in partial fulfillment through Eleanor Hung’s Master of Science in Epidemiology Degree at Queen’s University, Kingston.

Declarations of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.