Developing measures of fatigue using an alcohol comparison to validate theeffects of fatigue on performance

The effects of 28 h of sleep deprivation were compared with varying doses o f alcohol up to 0.1% blood alcohol concentration (BAC) in the same subjects . The study was conducted in the laboratory. Twenty long-haul truck drivers and 19 people not employed as professional drivers acted as subjects. Test s were selected that were likely to be affected by fatigue, including simpl e reaction time, unstable tracking, dual task, Mackworth clock vigilance te st, symbol digit coding, visual search, sequential spatial memory and logic al reasoning. While performance effects were seen due to alcohol for all te sts, sleep deprivation affected performance on most tests, but had no effec t on performance on the visual search and logical reasoning tests. Some tes ts showed evidence of a circadian rhythm effect on performance, in particul ar, simple reaction time, dual task, Mackworth clock vigilance, and symbol digit coding, but only for response speed and not response accuracy. Driver s were slower but more accurate than controls on the symbol digit test, sug gesting that they took a more conservative approach to performance of this test. This study demonstrated which tests are most sensitive to sleep depri vation and fatigue. The study therefore has established a set of tests that can be used in evaluations of fatigue and fatigue countermeasures. (C) 200 1 Elsevier Science Ltd. All rights reserved.