Modeling the relationship between shift work and cardiometabolic risk through circadian disruption, sleep and stress pathways

ABSTRACT

The purpose of this study is to elucidate the multiple pathways linking shift work exposure to cardiometabolic risk (CMR) through the intermediates of circadian disruption, sleep disturbances, and stress. A cross-sectional study was conducted at Kingston Health Sciences Center that included female hospital workers, 160 who worked a day-only schedule and 168 who worked rotating days and nights. Participants completed questionnaires, a clinical exam, and wore accelerometers to collect sleep data for 8 days. Participants also collected urine samples at each void during a 24-h collection period, on the day shift for day-only workers and the night shift for rotating shift workers, for cortisol and melatonin measures. We adapted and tested a conceptual model proposed by Knutsson and Boggild for circadian disruption, sleep, and stress mechanistic pathways linking shift work to CMR using structural equation modeling techniques. Status as a rotating shift worker was associated with increased circadian disruption of cortisol and melatonin production compared to day-only workers (P < .001). Increased circadian disruption was associated with an increased CMR (P = .01). Rotating shift work was associated with sleep disturbances (P = .002) and increased job stress (P < .001), but neither was associated with CMR. We conclude that rotating shift work is associated indirectly with increased CMR. This association is mediated by circadian disruption as indicated by attenuated melatonin and cortisol, and flatter cortisol curves.

KEYWORDS:

• Shift work
• circadian disruption
• cardiovascular risk
• mechanistic pathways
• metabolic syndrome

Acknowledgements

We thank the participants, the investigative team (L McGillis Hall, C Collier) involved in the design, staff (including R Corbin and C Kelly), and the students (including Michael Leung and Eleanor Hung) involved in data cleaning.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Grant Number

CIHR FRN 111023.

Patient consent

Obtained

Ethics approval

Queen’s University Health Sciences Research Ethics Board.

Additional information

Funding

This study was funded by the Canadian Institute for Health Research and the Workplace Safety and Insurance Board (Ontario).