Endocrine Abstracts

Introduction: The incidence of obesity and other features of the metabolic syndrome is increased in shift workers. This may be due to a misalignment between the internal circadian rhythm and the behavioral rhythm. The stress hormone cortisol could play a role in this phenomenon, because it is secreted in a circadian rhythm, and long-term elevated cortisol levels leads to components of the metabolic syndrome. Our aim was to study changes in long-term cortisol levels due to shift work.

Methods: This study consists of two parts. Part 1 (pilot study): hair samples were collected in 33 shift workers and 89 day workers. Height and weight were measured, and BMI was calculated¹. Part 2: hair samples were collected in 100 males working in shifts or only during the day. Hair samples were collected together with height, weight, hip and waist circumference and questionnaires concerning diet, exercise and perceived stress. Cortisol was extracted from the hair samples with methanol, and cortisol levels were measured using ELISA.

Results: Part 1: Hair cortisol levels were higher in shift workers than in day workers: 47.32 pg/mg hair (95% CI=38.37–58.21) vs 29.72 pg/mg hair (95% CI=26.18–33.73; P<0.001). When divided in age groups based on the median age, elevated cortisol levels were present particularly in younger shift workers: 48.53 pg/mg hair (95% CI=36.56–64.29) vs 26.42 pg/mg hair (95% CI=22.91–30.55) (P<0.001). BMI was increased in younger shift workers as well: 27.2 (95% CI=25.5–28.8) vs 23.7 (95% CI=22.8–24.7) in young day workers (P=0.001). Hair cortisol and BMI were positively correlated (β=0.262; P=0.005)¹. The results of the second part will be presented at the congress.

Conclusion: Shift work at young adult age is associated with elevated long-term cortisol levels and increased BMI. Elevated cortisol levels and BMI may contribute to the increased cardiovascular risk found in shift workers.

(1) Manenschijn et al. Shift work at young age is associated with elevated long-term cortisol levels and body mass index. J Clin Endocrinol Metab. 2011 Nov;96 (11) E1862–5.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.