New Research on Fatigue and Performance
Alexander (Sandy) Garden
Clinical Director Anaesthesia, Intensive Care and Pain Management, Wellington Hospital, Wellington.
Associate Professor and Clinical Associate Director, Sleep Wake Research Centre, Research School of Public Health, Massey University, Wellington.
Two aspects of recent research into the effects of fatigue and sleep loss will be discussed
The first relates to ongoing research into the effects of sleep loss upon performance on neuropsychological testing. It has been reliably shown that there is a cumulative dose-response relationship between sleep restriction and performance (1) and that after 17 hours of wakefulness the decrement in performance is similar to that produced by consumption of alcohol to the legal drink-drive limit (2). Interestingly, cumulative sleep-loss causes less decline in reaction-time among older individuals regardless of the degree of sleep restriction (3). In the context of anaesthesia, deterioration in neurocognitive testing has been shown in after a series of night shifts in anaesthetic registrars (4), indicating that current shift-work patterns in anaesthesia do not protect against performance decrement. The relationship between performance on neuropsychological testing and clinical performance remains an important and unanswered question.
The second aspect relates to effects of fatigue and sleep loss in the real world, including medical practice. There are clear data showing that the introduction of shift work and a reduction in hours of work for interns working in intensive care units, is associated with increased sleep, increased alertness and a reduction in error rate (5,6). In addition there are clear data showing an increased risk of accident while driving after extended duties in interns (7). In the general population there is an increase risk of accident while driving between 0200 and 0500, or driving after less than five hours sleep in the previous 24 hours (8), and this clearly applies to specialists who typically work on-call as opposed to registrars who work on-duty. More recently, in a national survey of all New Zealand junior doctors (registrars, senior house officers and house officers) 30% were judged excessively sleepy by Epworth Sleepiness Score. In this survey (n= 1366) 42% could recall making a fatigue-related clinical error in the previous six months, and 66% could recall feeling close to falling asleep while driving, in the previous 12 months. Unscheduled roster changes and three or more night duties in one of the previous two weeks were independent risk factors for recalling fatigue-related clinical error, whereas the perception of adequate supervision reduced the risk of both excessive sleepiness and error (9). These indicate that current work patterns do not prevent performance deterioration on “real-world” tasks, and show that there is more to consider than total hours worked.
References
1. Belenky G, Wesensten NJ, Thorne DR, Thomas MB, Sing HC, Redmond DP, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study. Journal of Sleep Research. 2003;12:1-12.
2. Dawson D, Reid K. Fatigue, alcohol and performance impairment. Nature 1977;388:253.
3. Bliese PD, Wesensten NJ, Balkin TJ. Age and individual variability in performance during sleep restriction. J Sleep Res. 2006 Dec;15(4):376-85.
4. Griffiths JD, McCutcheon C, Silbert BS, Maruff P. A prospective observational study of the effects of night duty on the cognitive function of anaesthetic registrars. Anaesth Intensive Care. 2006;34:621-8.
5. Landrigan CP, Rothschild JM, Cronin JW, Kaushal R, Burdick E, Katz JT, et al. 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.
6. Lockley SW, Cronin JW, Evans EE, Cade BE, Lee CJ, Landrigan CP, et al. Effect of reducing interns' weekly work hours on sleep and attentional failures. N Engl J Med. 2004 Oct 28;351(18):1829-37.
7. Barger LK, Cade BE, Ayas NT, Cronin JW, Rosner B, Speizer FE, et al. Extended work shifts and the risk of motor vehicle crashes among interns. N Eng J Med. 2005;352(2):125-34.
8. Connor J, Norton R, Ameratunga S, Robinson E, Civil I, Dunn R, et al. Driver sleepiness and risk of serious injury to car occupants: population based case control study. BMJ. 2002 May 11;324(7346):1125.
9. Gander P, Purnell H, Garden A, Woodward A. Work patterns and fatigue-related risk amongst junior doctors. Occupational and Environmental Medicine. 2007;in press.
Time of Presentation
1330
