Effects of Night Shift Work on Nighttime Blood Pressure among Healthy Young Female Medical Workers

Background Although night shift is an independent risk factor of cardiovascular disease (CVD), the underlying mechanisms have not been understood. Nocturnal blood pressure (BP) and increased BP variability are associated with CVD. However, little is known regarding the impact of night shift on nocturnal BP variables. Methods The study population consisted of 30 healthy female medical shift workers (mean age, 28±6 years) with flexible blood vessels (mean cardio-ankle vascular index, 5.8±0.9). Nocturnal BP variables were measured after day and night shifts using a home BP monitoring device. Similarly, sleep status (total sleep time, sleep efficiency, and snoring) were measured using a noncontact radiofrequency sensor. Results Nocturnal diastolic BP variability (7.0±5.3 mm Hg vs 4.7±2.7 mm Hg; p<0.01) was significantly higher after night shift than after day shift, whereas no significant differences in systolic BP variables, mean diastolic BP, and sleep status were observed. Conclusions Among young healthy women with flexible blood vessels, night shift increased nighttime diastolic BP variability, rather than systolic BP variables independent of sleep disorder. These findings imply that increased nighttime diastolic BP variability derived from night shift might stimulate an early- stage atherosclerotic process that predisposes patients to future CVD.