Objective: The aim of the field study was to objectify physicians' vigilance, well-being, and cognitive performance in the course of 24-hr shifts with and without afternoon rest. SUBJECTS, SETTING, AND DESIGN: Eleven residents (four women, seven men; age, 33.5 +/- 4.7 yrs) were observed when doing two regular 24-hr shifts at the emergency department (randomized crossover design): one without rest, the other with a period of rest in the early afternoon (duration, 2:31 +/- 1:04 hrs) and the opportunity of having a nap (duration, 1:07 +/- 0:26 hrs, n = 6). Electroencephalography and psychometric tests were carried out at 8 am and at midnight.
Measurements: Measurements included subjective perception of workload, stress, and sleeping behavior; computer-analyzed electroencephalography; adjective checklist (Eigenschaftswörterliste 60 S, a self-rating scale); complex reaction time test; Pauli test (number of calculations during 3 mins); and numerical memory test.
Results: Electroencephalographic analyses showed a significant decrease in alpha power and a significant increase in beta power in the evening as compared with the morning on both days. The nocturnal increase observed in delta activity was significantly less pronounced in duties with rest than in duties without rest. Physicians felt deactivated at night. The Eigenschaftswörterliste 60 S indicated deactivation at night and a rest-induced activation in the subgroup that had taken the opportunity to sleep in the afternoon. Psychometric tests did not show any significant differences, neither between performance in the morning and evening nor between results with and without rest.
Conclusion: As expected, electroencephalographic recordings showed nocturnal deactivation and a vigilance-promoting effect of the afternoon rest. These objective findings were in accordance with the results derived from self-rating scales. On the other hand, in short-lasting psychometric tests, performance was found unchanged after 16 hrs of routine work. In further studies, a discrimination between resting periods with and without sleep will be important.