Hemostatic markers in shift working female nurses

Abstract

Studies indicate an increased risk of cardiovascular disease (CVD) among shift workers, yet the mechanisms underlying this relationship are not well understood. The hemostatic system significantly impacts CVD, and several hemostatic markers demonstrate circadian rhythmicity. Thus, circadian misalignment of hemostatic markers due to shift work may be involved in the increased risk of CVD. This study aimed to compare hemostatic markers among healthy shift working vs. daytime working female nurses. It was hypothesized that hemostatic markers are elevated in shift compared to day workers, beyond the effects of sleep disturbance and other factors known to detrimentally affect health in shift workers. Thirty shift and 30 day working female nurses ages 30–45 were recruited by quota sampling at Rambam Health-Care Campus. Nurses were included if they were healthy, did not smoke, had a BMI¡‘Ü26, had no family history of CVD at a young age, were not using medication regularly (except oral contraceptives), did not have a fever in the past month and were not pregnant. Shift workers had at least two non day shifts and one night shift per week. For all participants, blood was drawn at 07:00 in the morning (not following a night shift) for the measurement of seven markers of coagulation, including Plasminogen activator inhibitor-1 (PAI-1), heparanase procoagulant activity, tissue factor (TF) + heparanase complex, protein C, D- dimer, Von Willebrand factor (vWF) and fibrinogen. Sleep quality was assessed by self report (Pittsburgh Sleep Quality Index). All coagulation markers were in the normative range. PAI-1 levels were significantly higher among shift compared to day workers (36.6 ng/ml vs 24.3 ng/ml, p < 0.05). In shift workers, Heparanase procoagulant activity was 2- fold and TF + heparanase complex was 1.5-fold compared to day work nurses (both p < 0.05). Sleep quality was significantly lower for shift compared to day workers ( p < 0.001). No group differences were found for Protein C, D-dimer, vWF and fibrinogen. Logistic regression analyses showed that shift work and poor sleep quality were significant predictors of high levels of PAI-1 ( R 2 = 0.17), heparanase procoagulant activity ( R 2 = 0.13) and TF + heparanase ( R 2 = 0.10). Elevated levels of PAI-1 and heparanase markers in healthy shift working nurses suggest subclinical disturbances in the hemostatic system, which together with reduced sleep quality may contribute to future cardiovascular morbidity. The authors acknowledge the support and assistance of the coagulation laboratory at Rambam Health Care Campus .