Shiftwork, sleep disturbances and cardiometabolic risk in female hospital employees
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Background: Epidemiologic evidence supports the association between shiftwork and the development of cardiovascular disease. Sleep disturbances are associated with a variety of adverse cardiometabolic outcomes and they may lie on the causal pathway between the exposure to shiftwork and cardiovascular disease. Objectives: 1) To describe sleep quality in a group of shift-working and day-working female hospital employees; 2) To determine the association between shiftwork status and sleep disturbances in this group and to determine the effect of lifetime exposure to shiftwork on current sleep disturbances; and 3) To explore whether sleep disturbances mediate the relationship between shiftwork and cardiometabolic risk. Methods: A cross-sectional study was conducted among female hospital employees: participants were 132 women working only during the day, and 98 women who worked a shift schedule of two 12-hour days, followed by two 12-hour nights and five days off. Sleep quality was assessed with the Pittsburgh Sleep Quality Index questionnaire. The primary outcome of interest was the metabolic syndrome defined in accordance with the 2009 Joint Interim Studies consensus statement. Results: Shiftwork was associated with poor sleep latency (odds ratio (OR)= 2.08 95% CI: 1.11-3.92), poor sleep efficiency (OR=2.35 95% CI: 1.21- 4.54), and poor global sleep quality (OR=1.88 95% CI: 1.02-3.49), while the impact of past shiftwork history was inconclusive. The OR for the association of shiftwork with the metabolic syndrome was 2.00 (95% CI: 0.89-4.51), and there was no evidence of mediation by sleep disturbances in the relationship of shiftwork and the metabolic syndrome. Conclusion: In this study, a rapid forward rotating 2-shift system is associated with self-reported poor sleep quality, while the long-term effects of sleep disturbances on cardiometabolic risk requires further study.