March 14, 2016

Article Review

While the working hours of occupations such as airline pilots fhave been regulated for decades, similar regulations regarding physician residents have been introduced only recently in Europe. The main underlying reasons for these regulations were to adequately address the effects of fatigue on professional performance and medical errors and to enhance quality of care and patient centered outcomes. However, to date, there are no regulations concerning the age limit of physicians performing night shifts. A large randomised-controlled trial published in 2004 suggested that extended working hours for residents led to increasing serious medical errors in diagnosis and administration of medication and non-intercepted medical errors [1]. Data on the impact of physician age on medical performance as well as the impact of sleep duration during the night shift are still lacking.

The authors of this recent study published in Intensive Care Medicine (March, 2016) sought to compare the cognitive performance of intensivists after a night shift vs. a night of rest and to determine whether it was influenced by physician experience (senior vs. resident) or sleep duration. In this prospective randomised cross-over study, each physician was her/his own control. Four cognitive abilities were studied after a night shift and after a night of rest at home: working memory capacity, perceptual reasoning, processing speed (each evaluated through one subtest of the Wechsler Adult Intelligence Scale) and cognitive flexibility (evaluated through the Wisconsin Card sorting test). All evaluations were conducted similarly by the same psychologist.

The majority of medical staff (88%) from three French academic ICUs participated in the study. 51 subjects (24 seniors and 27 residents) were included, average age of 32±7.3, majority female (n=28, 55%), with an average number of 5.5± years in the specialty and performing on average 4.8±1.4 nights per month. Senior intensivists were more likely to sleep during the night shift than residents (4.15 vs. 2.6h) and this was partly related to reduced numbers of phone wake ups (1.42 vs. 2.81) and stand ups (0.36 vs. 1). On average, all cognitive abilities were significantly decreased after a night shift, regardless of sleep duration. But the observed differences remain in the mean ± 1 SD of the performance of reference population. Perceptual reasoning was the lonely cognitive performance influenced by physician experience (significantly lower for residents after a night shift).

This is a well conducted study that uses validated psyco cognitive assessment scales to measure cognitive abilities of intensivists in real working conditions.

The main limitations that deserve attention, acknowledged by the authors, are the young age of study participants and that the results were not correlated to decreased clinical performances or poorer quality of care, which are more relevant for patients.  

Take home message
Intensivists cognitive abilities are decreased after a night shift regardless of the sleep duration during the shift.

Article review was prepared by Yên-Lan Nguyen.


1. Landrigan CP, Rothschild JM, Cronin JW, Kaushal R, Burdick E, Katz JT, Lilly CM, Stone PH, Lockley SW, Bates DW, Czeisler CA: Effect of reducing interns' work hours on serious medical errors in intensive care units. N Engl J Med. 2004 Oct 28;351(18):1838-48.

2. François Maltese, Mélanie Adda,  Amandine Bablon, Sami Hraeich, Christophe Guervilly, Samuel Lehingue, Sandrine Wiramus, Marc Leone, Claude Martin, Renaud Vialet, Xavier Thirion, Antoine Roch, Jean-Marie Forel, Laurent Papazian. Night shift decreases cognitive performance of ICU physicians. Intensive Care Medicine, Original, Volume 42, Issue 3 / March, 2016, Pages 393 – 400

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