[28] Amir O, Alroy S, Schliamser JE, Asmir I, Shiran A, Flugelman MY, Halon DA, Lewis BS. Brachial artery endothelial function in residents and fellows working night shifts. Am J Cardiol. 2004 Apr 1;93(7):947–9. doi: 10.1016/j.amjcard.2003.12.032. PMID: 15050508. RefID—15 PMID—15050508
Study Setting	Lady Davis Carmel Medical Center in Israel
Eligible Participants	The study group consisted of 30 healthy physicians (35 ± 4 years of age, range 28 to 45), including 17 internal medicine, five surgery residents, and eight fellows (six cardiology, one gastroenterology, and one hematology).
Study Aims	To examine the effect of night duty, with its inevitable stresses and lifestyle changes, on endothelial function in apparently healthy physicians.
Study Design & Participants	The average duration of the physicians who had worked night shifts at the time of the study was 5 years ± 3 years (range 0.5 to 15). None of the physicians had a history of coronary artery disease, diabetes mellitus, or hypertension. Two physicians were receiving cholesterol-lowering medications (statins), and six were smokers. Investigators used an observational study design comprised of two days (approximately) of observation and data collection. The primary outcome of interest was endothelial function, which was examined twice for each subject: (1) on a regular workday (with no previous or subsequent night shift, defined as baseline measurement of FMD), and (2) after a continuous workday of 24 h, including a night shift. All examinations were performed in the morning (8 to 10 a.m.) under identical conditions in a temperature-controlled room (20 °C to 25 °C). After the shift, physicians completed a questionnaire regarding the shift, including number of hours slept, estimated difficulty of the shift (on a 1 to 10 scale), and level of coffee consumption (number of cups during the shift). Cigarette smoking during the shift was not quantified because smoking is not permitted within the facility. Sleep was documented with a questionnaire.
Intervention/Exposure	Participants completed a night shift (24 h in duration) and sleeping during night shifts was measured post-night shift with a questionnaire.
Comparison(s)	After a 24 h shift (which included night shift work), FMD was measured and compared to a baseline measurement taken on a regular workday.
Outcome Measure(s)	The primary outcome of interest was endothelial function as measured via FMD: (%) = [(D2 − D1)/D1] × 100, where D2 is the reactive hyperemia diameter and D1 is the baseline diameter. In addition, investigators used nitrate-mediated dilation with sub-lingual spray of 400 ug glyceryl trinitrate. Authors reported main findings in Figure 1, showing the impact of night shift exposure on FMD.
Key Finding(s)	Following use of multivariate stepwise regression analyses, as reported in Table 2 of Amir et al., 2004 [28], investigators show that the fewer number of sleeping hours during the shift was associated with greater decrease in FMD post-24 h shift compared to baseline FMD measure (p = 0.03). In addition, authors show that the decrease in FMD after the 24 h shift was independently related to a longer history of shift work (p = 0.0008).