title: Working the night shift causes increased vascular stress and delayed recovery in young women.
abstract: Shiftwork has been associated with elevated blood pressure (BP) and decreased heart-rate variability (HRV), factors that may increase the long-term risk of cardiovascular-related mortality and morbidity. This study explored the effect of shiftwork on dynamic changes in autonomic control of HRV (cardiac stress), systolic BP and diastolic BP, i.e., SBP and DBP (vascular stress), and recovery in the same subjects working different shifts. By studying the same subjects, the authors could reduce the effect of possible contribution of between-subject variation from genetic predisposition and environmental factors. The authors recruited 16 young female nurses working rotating shifts--day (08:00-16:00 h), evening (16:00-00:00 h), and night (00:00-08:00 h)--and 6 others working the regular day shift. Each nurse received simultaneous and repeated 48-h ambulatory electrocardiography and BP monitoring during their work day and the following off-duty day. Using a linear mixed-effect model to adjust for day shift, the results of the repeated-measurements and self-comparisons found significant shift differences in vascular stress. While working the night shift, the nurses showed significant increases in vascular stress, with increased SBP of 9.7 mm Hg. The changes of SBP and DBP seemed to peak during waking time at the same time on the day off as they did on the working day. Whereas HRV profiles usually returned to baseline level after each shift, the SBP and DBP of night-shift workers did not completely return to baseline levels the following off-duty day (p < .001). The authors concluded that although the nurses may recover from cardiac stress the first day off following a night shift, they do not completely recover from increases in vascular stress on that day.
authors.affiliation: Department of Internal Medicine, Zhongxing Branch of Taipei City Hospital, Taipei, Taiwan.
authors.forename: Shih-Hsiang
authors.initials: SH
authors.lastname: Lo
authors.forename: Lian-Yu
authors.initials: LY
authors.lastname: Lin
authors.forename: Jing-Shiang
authors.initials: JS
authors.lastname: Hwang
authors.forename: Yu-Yin
authors.initials: YY
authors.lastname: Chang
authors.forename: Chiau-Suong
authors.initials: CS
authors.lastname: Liau
authors.forename: Jung-Der
authors.initials: JD
authors.lastname: Wang
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D013312:Stress, Physiological; D014940:Work Schedule Tolerance / Q000502:physiology*
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