If you sleep six hours a night for twelve days, Adusumilli says—and that’s about how much many Americans sleep all year round—your cognitive and physical performance becomes virtually indistinguishable from that of someone who has been awake for twenty-four hours straight. (The same effect is produced by six days of four-hour nights.) And the performance of someone who has been awake for twenty-four hours straight is similar to that ofsomeone with a blood alcohol level of 0.1 per cent. In other words, “normal” amounts of sleep deprivation have us acting like we’re drunk.
In the short term, these types of deficits have a significant effect on our performance across the board. Perception deteriorates, along with motor skills: in one study of college basketball players, well-rested players performed better than those who followed their usual schedules. Emotional control suffers—the connection between the prefrontal cortex (where we make executive decisions) and the amygdala (which is associated with fear and other emotions) degrades—and we become more impulsive and prone to depression. And our ability to think and to make sound decisions plummets. We become worse at learning, memory, and simple tasks of arithmetic and analytic reasoning. The rate of accidents and errors rises. In one study, which compared first-year interns at Brigham and Women’s Hospital who worked on a regular schedule to those working on shorter, sixteen-hour shifts that included a nap, the sleep-deprived residents made more than double the number of attentional errors at night—a result that has been replicated multiple times. [link]