J. Sleep Res. (1999) 8, 255–262 Quantifying the performance impairment associated with fatigue NICOLE LAMOND and DREW DAWSON The Centre for Sleep Research, The Queen Elizabeth Hospital, South Australia Accepted in revised form 1 June 1999; received 21 November 1998 SUMMARY The present study systematically compared the eﬀects of fatigue and alcohol intoxication on a range of neurobehavioural tasks. By doing so, it was possible to quantify the performance impairment associated with fatigue and express it as a blood alcohol impairment equivalent. Twenty-two healthy subjects aged 19–26 years participated in three counterbalanced conditions. In the sustained wakefulness condition, subjects were kept awake for 28 h. In the alcohol and placebo conditions, subjects consumed either an alcoholic or non-alcoholic beverage at 30 min intervals, until their blood alcohol concentration reached 0.10%. In each session, performance was measured at hourly intervals using four tasks from a standardised computer- based test battery. Analysis indicated that the placebo beverage did not signiﬁcantly eﬀect mean relative performance. In contrast, as blood alcohol concentration increased performance on all the tasks, except for one, signiﬁcantly decreased. Similarly, as hours of wakefulness increased performance levels for four of the six parameters signiﬁcantly decreased. More importantly, equating the performance impairment in the two conditions indicated that, depending on the task measured, approximately 20–25 h of wakefulness produced performance decrements equivalent to those observed at a blood alcohol concentration (BAC) of 0.10%. Overall, these results suggest that moderate levels of fatigue produce performance equivalent to or greater than those observed at levels of alcohol intoxication deemed unacceptable when driving, working and/or operating dangerous equipment.  alcohol intoxication, performance impairment, sustained wakefulness INTRODUCTION By contrast, the impairing eﬀects of alcohol intoxication are generally well accepted by the community and policy makers, The negative impact of sleep loss and fatigue on resulting in strong enforcement of laws mandating that neurobehavioural performance is well documented (Gillberg individuals whose blood alcohol concentration exceeds a certain et al. 1994; Mullaney et al. 1983; Tilley and Wilkinson 1984). level be restricted from driving, working and/or operating Studies have clearly shown that sustained wakefulness dangerous equipment. Consequently, several studies have used signiﬁcantly impairs several components of performance, alcohol as a standard by which to compare impairment in including response latency and variability, speed and accuracy, psychomotor performance caused by other substances (Dick hand-eye coordination, and decision-making and memory et al. 1984; Heishman et al. 1989; Thapar et al. 1995). By using (Babkoﬀ et al. 1988; Fiorica et al. 1968; Linde and Bergstrom alcohol as a reference point, such studies have provided more 1992). Nevertheless, understanding of the relative performance easily grasped results regarding the performance impairment decrements produced by sleep loss and fatigue among policy- associated with such substances. makers, and within the community, is poor. In an attempt to provide policy makers and the community with an easily understood index of the relative risks associated with sleep loss and fatigue, Dawson and Reid (1997) equated Correspondence: Drew Dawson, The Centre for Sleep Research, The the performance impairment of fatigue and alcohol intoxication Queen Elizabeth Hospital, Woodville Road, Woodville SA 5011, using a computer-based unpredictable tracking task. By doing Australia. Tel.:+61 88222 6624; Fax:+61 88222 6623; e-mail: drew.dawson@unisa.edu.au so, the authors demonstrated that one night of sleep deprivation 255  1999 European Sleep Research Society