From Dement's The Promise of Sleep:
"In his latest research, University of Pennsylvania fatigue expert David Dinges restricted the sleep of volunteers over a two-week period. David concluded that when people sleep only four hours a night for two weeks, their performance scores are the same as those of people who were kept up for three straight days and nights.
Dave found that within his test group, individual sensivity to sleep load initially varied widely, much the way people's susceptibility to alcohol does. But at the end of the two-week period, everyone was seriously imparied by long-term sleep debt.
Dave and the other researchers have demonstrated that chronic sleep loss degrades nearly every aspect of human performance: vigilance (ability to receive information, alertness (ability to act on information), and attention span. In simple terms, a large sleep debt "makes you stupid." People take longer to react to challenging situations, and their reactions are more variable and less effective than when they are well rested....
....The comparison between sleep deprivation and alcohol intoxication is striking in this regard. Researchers in Australia have found that there is a more than just a surface similarity between the two. The Australian investigators split 40 volunteers into two groups. One group was kept awake for 28 hours, from 8:00 A.M. until 2:00 P.M. the next day. The other group was given 10 to 15 grams of alcohol every 30 minutes starting at 8:00 A.M., until each volunteer's blood alcohol level reached 0.1 percent, which is more than legally drunk in most locales. During these periods, both groups were given hand-eye coordination tests. The Australian researchers found that after 17 hours awake (at 1:00 A.M, when biological alerting is declining), the sleep-deprived group had the same test scores as drinking volunteers who had blood-alcohol levels of 0.05 percent. After 24 hours awake, the sleep-deprived group had the same coordination deficits as those with the maximum blood-alcohol level, 0.1 percent...." (pg. 231-232)