A note of caution for those working excessive overtime: Being awake for 17 to 19 hours roughly equates to a blood alcohol content of .05, according to a study by Dr. Ann Williamson of the University of New South Wales. The Australian study looked at fatigue's effects on cognitive and motor speed, accuracy, coordination and attention. Reaction time on some tests was up to 50 percent worse in the sleep deprivation condition than the alcohol condition.