Influence of Shift Duration on Cognitive Performance of Emergency Physicians: A Prospective Cross-Sectional Study.

STUDY OBJECTIVE: The relationship between tiredness and medical errors is now commonly accepted. The main objective of this study is to evaluate the cognitive performance of emergency physicians after a night shift of 14 hours (H14) and after a work shift of 24 hours (H24) and to compare it with tests performed after a rest night at home (H0).

METHODS: Forty emergency physicians (19 staff physicians and 21 residents) were randomly evaluated at H0, H14, and H24. Four cognitive abilities (processing speed, working memory capacity, perceptual reasoning, and cognitive flexibility) were tested according to the Wechsler Adult Intelligence Scale and the Wisconsin Card Sorting Test.

RESULTS: No cognitive ability was significantly altered after H14 compared with H0. Three of 4 cognitive abilities were impaired at H24 compared with H0: processing speed (11.2 [SD 2.7] versus 12.4 [SD 3.2]; mean difference=-1.2 [95% confidence interval -1.9 to -0.5]), working memory capacity (10.1 [SD 2.9] versus 11.6 [SD 3.0]; mean difference=-1.5 [95% confidence interval -2.2 to -0.8]), and perceptual reasoning (8.4 [SD 2.7] versus 10.6 [SD 2.8]; mean difference=-2.2 [95% confidence interval -3.4 to -1.0]). Cognitive abilities were not different between residents and staff physicians (except for perceptual reasoning) and were not affected by the amount of sleep during the night shift.

CONCLUSION: The cognitive abilities of emergency physicians were significantly altered after a 24-hour shift, whereas they were not significantly different from the rested condition after a 14-hour night shift. Limiting 24-hour shift work for emergency physicians should be considered and further evaluated.