Modelling the relationship between shift work and cardiometabolic risk through circadian disruption, sleep and stress pathways
Aim and objectives: The aim of this research was to use structural equation modelling methods to test an adaption of the model proposed by Knutsson and Boggild, and to elucidate and determine the multiple pathways linking shift work exposure to cardiometabolic risk through the intermediates circadian disruption, sleep disturbances, and stress. The specific objectives were: 1) To produce a measurement model of the following latent variables: circadian disruption, sleep disturbances, and cardiometabolic risk, with adequate fit parameters; (2) To investigate the hypothesized structural model of mechanisms linking work status and shift work duration with cardiometabolic risk: (a) To determine the fit of the hypothesized model to observed data; and (b) To identify estimates of partial correlation between variables. Methods: A cross-sectional study was conducted at the Kingston Health Sciences Centre (2011-2014) with 168 rotating shift workers and 160 day-only female workers completing self-report questionnaires, a clinical exam, 8 day accelerometer collection, and each urinary void over a 48-hour period. Validated measures were determined for psychological job stress, life stress, cardiometabolic risk, sleep and melatonin and cortisol production. A conceptual model based on a hypothesized model of physiological, behavioral and social pathways of potential mechanisms linking shift work to cardiometabolic risk through these intermediates was then adapted and tested using structural equation modelling. Results: Status as a rotating shift worker was indirectly associated with cardiometabolic risk through circadian disruption. Specifically, status as a rotating shift work was associated in the day model with a 0.30 standard deviation (SD) increase in circadian disruption, and in the night model a 0.85 SD increase. Increased circadian disruption was also associated with an increase in cardiometabolic risk (0.47 SD for day model, 0.27 SD for night model). Shift work status was also associated with a 0.24 SD increase in sleep disturbances and a 0.26 SD increase in job stress, but these intermediates were not associated with cardiometabolic risk. Shift work duration was not associated with any intermediate. Conclusion: Status as a rotating shift worker is indirectly associated with cardiometabolic risk, and this relationship is primarily mediated by circadian disruption.