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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.

Night work has emerged as a risk factor for many chronic diseases, including obesity, diabetes, and cardiovascular disease. While night work is linked to a number of cardiometabolic indices, few studies have explored how different parameters, such as cumulative night work and intensity of night work, may influence cardiometabolic risk. Fewer studies have also explored the relationship while considering chronotype, a potential modifier between shift-induced circadian disruption and cardiometabolic outcomes. The main objective is to determine the association between night work parameters and cardiometabolic risk factors. The secondary objective is to assess how the association between night work parameters and cardiometabolic risk factors differs by chronotype. A cross-sectional study was conducted with 325 full- and part-time female hospital employees (168 rotating night workers, 157 day workers). Night work status, cumulative night work duration, and night work intensity were determined through self-report, and cardiometabolic risk factors were assessed through clinical exams. Chronotype was determined using the Munich Chronotype Questionniare (MCTQ). Multiple linear regression was used to examine the association between night work parameters and cardiometabolic risk factors. Current night work, cumulative night work, and night work intensity are associated with a number of cardiometabolic indices, including higher waist circumference, body mass index, fasting glucose, blood pressure, and cardiometabolic risk score. When stratified by chronotype, night work parameters are associated with a number of cardiometabolic risk factors in the evening-oriented chronotype subgroup. There is no difference in cardiometabolic risk factors in morning-oriented chronotypes when comparing night work parameters, with the exception of LDL cholesterol. These results suggest that night work parameters are associated with cardiometabolic risk, and night workers with an evening-oriented chronotype may be more susceptible to the adverse cardiometabolic impacts of night work. Future studies should consider chronotype when examining the relationship between night work and cardiometabolic risk.

Background: Shift work is a risk factor for many diseases, including cardiovascular disease. Although the biological pathways are still unclear, it is hypothesized that cortisol disruption during night work is an intermediate. The objective of this study is to determine whether total cortisol production and cortisol pattern mediate the relationship between current shift work and cardiometabolic risk (CMR) among female hospital employees., Methods: A cross-sectional study was conducted among 326 female employees (166 rotating shift workers, 160 day workers), recruited from a hospital in Southeastern Ontario, Canada, during 2011 to 2014. Participants completed a baseline interview, questionnaire, and clinical exam. Urine samples were collected over two 24-hour periods and used to analyze creatinine-adjusted cortisol, which was then used to calculate total cortisol production (AUC G ), and pattern (AUC I ). Mediation analysis was performed to test the mediating effect of cortisol in the relationship between shift work and a continuous CMR score., Results: Current shift work is associated with a 0.52 higher CMR score (95% CI: 0.15, 0.89), a lower cortisol output (AUC G ), and a flatter pattern (AUC I ) over a 2-day period. AUC G is a partial mediator in the relationship between shift work and CMR, whereas AUC I is not. AUC G is also associated with CMR while controlling for shift work, suggesting that lower total cortisol production is also linked to CMR in non-shift workers., Conclusions: Total cortisol production is a partial mediator in the relationship between rotating shift work and CMR among female hospital employees, whereas cortisol pattern is not a mediator., (Copyright © 2018 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Objective: This study explored the associations between work patterns and indicators of cardiometabolic risk in female hospital employees., Background: Aspects of work environments potentially influence the health of employees; however, we have a poor understanding of how different hospital work patterns contribute to cardiovascular risk in female employees., Methods: We conducted a cross-sectional study of 466 female employees from 2 hospitals in Ontario. Data were collected through self-report, physical examination, and use of hospital administrative work data., Results: In the adjusted analyses, full-time work status, extended shift length, and working 35 or more paid overtime hours per year were significantly associated with metabolic syndrome., Conclusions: Different work patterns increase cardiometabolic risk in female employees, suggesting a need to better monitor the health of the workforce and implement healthy workplace policy.