• Hsiu-Hao Lee, Shih-Hsiang Lo, Bing-Yu Chen, Yen-Hung Lin, Dachen Chu, Tsun-Jen Cheng, Pau-Chung Chen, and Yue-Liang Guo.
• Institution of Occupational Medicine and Industrial Hygiene, National Taiwan University College of Public Health, Taipei, Taiwan.
• Int Arch Occup Environ Health. 2016 Apr 1; 89 (3): 413-23.

PurposeNight duty has been recognized as a significantly harmful stressor for physicians. However, the relationship between various levels of duty loading and stress response is unknown. This study examined whether duty load increases cardiovascular stress indicators in a dose-dependent manner.MethodsAn unallocated prospective observational study was conducted among physicians performing various levels of duties in a secondary referral medical center between 2011 and 2012. Heart rate variability (HRV), blood pressure (BP), and other stress markers of 12 attending physicians were compared during different duty loads: non-duty day (NDD), duty day with one duty area and three wards (1DD), and duty day with two duty areas and six wards (2DD).ResultsDuring the regular sleep time (i.e., 11 p.m. to 5 a.m.), the relative sympathetic modulations measured using the HRV were 59.0 ± 9.3, 61.6 ± 10.4, and 64.4 ± 8.9 for NDD, 1DD, and 2DD, respectively (p = 0.0012); those for relative parasympathetic modulations were 37.4 ± 9.4, 34.8 ± 9.8, and 32.0 ± 8.8 for NDD, 1DD, and 2DD, respectively (p = 0.0015). The percentages of abnormal systolic BPs were 9.7 ± 13.2 %, 25.3 ± 21.8 %, and 31.5 ± 21.0 % for NDD, 1DD, and 2DD, respectively (p = 0.003), and the percentages of abnormal diastolic BP were 6.7 ± 11.0 %, 18.3 ± 11.1 %, and 27.1 ± 30.9 % for NDD, 1DD, and 2DD, respectively (p = 0.002). Total sleep time was negatively associated with sympathetic/parasympathetic balance and the percentage of abnormal diastolic BP. Admitting new patients was positively associated with the percentages of abnormal systolic BP.ConclusionsThis observational analysis suggests that the dose-dependent stress responses of the cardiovascular system in physicians were caused by the duty load.

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