Lack of Sleep - H&S no2

Lack of sleep is dangerous

A recently published Australian study compared the relative effects on performance of sleep deprivation and alcohol. Performance effects were studied in the same subjects over a period of 28 hours of sleep deprivation and after measured doses of alcohol up to about 0.1% blood alcohol concentration (BAC). There were 39 subjects, 30 employees from the transport industry and nine from the army. After 17-19 hours without sleep, corresponding to 10:30 pm and 1:00 am after waking at 6 am, performance on some tests was equivalent or worse than that at a BAC of 0.05%. Response speeds were up to 50% slower for some tests and accuracy measures were significantly poorer than at this level of alcohol. The tests included passive vigilance, reaction time, hand-eye coordination, divided attention, remembering numbers, special memory, memory and grammatical reasoning. After longer periods without sleep, performance reached levels equivalent to the maximum alcohol dose given to subjects (BAC of 0.1%). The investigators concluded that the findings reinforce the evidence that the fatigue of sleep deprivation is an important factor likely to compromise performance of speed and accuracy of the kind needed for safety on the road and in other industrial settings.

1 Williamson AM, and AM Feyer,. “Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication.” Occup Environ Med. 2000 Oct; 57(10):649-655.

UAW Commentary on Sleep Deprivation

This paper adds to a large and diverse scientific literature on psychomotor performance in relation to work schedule (extended duty, rotating and night shift work), fatigue, chemical exposure and medicinal drug use. Recent actions in this area include the European Union Directive on Hours of Work, regulation of truck driver schedules now before DOT, and some state legislation. This study gives quantitative expression to our impressions that tired people are prone to mistakes which pose injury risks. The study measured time since waking, rather than time at work, and reported only the duration (17 hrs) for very substantial decrements. In UAW experience, test batteries of this type are insensitive to symptoms of solvent exposure. Another study reported an increase in errors in power plant operators at the end of a 12 hour shift (among employees who otherwise preferred a 12 hour to 8 hour schedule.)1 Since workers in a comparable fatigue state are now and will likely be working in industrial settings for the foreseeable future, safety systems must be designed to tolerate the errors of persons in attention states equivalent to legally intoxicated. If limits on work duration are prescribed as a safety measure, the limit should trigger before the performance decrement becomes statistically significant.

1 Mitchell RJ and AM Williamson. “Evaluation of an 8 hour versus a 12 hour shift roster on employees at a power station.” Appl Ergon. 2000 Feb;31(1):83-93.

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