Extended Wakefulness, Combined With Alcohol, Severely Impairs Driving Performance

The study, authored by Mark E. Howard, PhD, of the Institute for Breathing and Sleep in Heidelberg, Victoria, Australia, focused on 19 volunteer professional drivers, who participated in a driving simulation and the Psychomotor Vigilance Task.

The subjects were measured in a rested state (12-15 hours awake) and after extended wakefulness (18-21 hours awake) during two sessions. Alcohol was administered during one session, with performance measured at blood alcohol concentrations (BAC) of 0.00 percent, 0.03 percent and 0.05 percent in a non-sleep deprived state, and at 0.03 percent after extended wakefulness (at 1 a.m. and at 3 a.m.). During the second session, tests were performed at the same times without alcohol.

According to the results, extended wakefulness, combined with low-dose alcohol (0.03 percent BAC), resulted in more lapses and greater variation in lane position and speed than did a BAC of 0.05 percent in a rested state.

"In addition to alcohol, sleepiness also increases the risk of road crashes. It is estimated that 15 to 30 percent of traffic accidents are directly related to driver sleepiness, as determined by crash circumstances. Although there are conclusive data regarding the separate effects of alcohol and sleepiness on driving, in real-life situations it is common for these two conditions to occur simultaneously (alcohol-related accidents occur more commonly in the early hours of the morning). The combination of legal low-dose alcohol and extended wakefulness results in impairment worse than that at an alcohol level known to increase accident risk. Avoiding alcohol when driving after extended wakefulness may reduce accident risk," said Dr. Howard.

Article: "The Interactive Effects of Extended Wakefulness and Low-Dose Alcohol on Simulated Driving and Vigilance"