From David K. Randall, discussing the sometimes heard that sleeping in shifts might be best:
Any stories? Kris and I both wake up every night, sometimes for just a few minutes but often for 30 minutes or more. How about you?
Typically, mention of our ever increasing sleeplessness is followed by calls for earlier bedtimes and a longer night’s sleep. But this directive may be part of the problem. Rather than helping us to get more rest, the tyranny of the eight-hour block reinforces a narrow conception of sleep and how we should approach it. Some of the time we spend tossing and turning may even result from misconceptions about sleep and our bodily needs: in fact neither our bodies nor our brains are built for the roughly one-third of our lives that we spend in bed.
The idea that we should sleep in eight-hour chunks is relatively recent. The world’s population sleeps in various and surprising ways. Millions of Chinese workers continue to put their heads on their desks for a nap of an hour or so after lunch, for example, and daytime napping is common from India to Spain.
One of the first signs that the emphasis on a straight eight-hour sleep had outlived its usefulness arose in the early 1990s, thanks to a history professor at Virginia Tech named A. Roger Ekirch, who spent hours investigating the history of the night and began to notice strange references to sleep. A character in the “Canterbury Tales,” for instance, decides to go back to bed after her “firste sleep.” A doctor in England wrote that the time between the “first sleep” and the “second sleep” was the best time for study and reflection. And one 16th-century French physician concluded that laborers were able to conceive more children because they waited until after their “first sleep” to make love. Professor Ekirch soon learned that he wasn’t the only one who was on to the historical existence of alternate sleep cycles. In a fluke of history, Thomas A. Wehr, a psychiatrist then working at the National Institute of Mental Health in Bethesda, Md., was conducting an experiment in which subjects were deprived of artificial light. Without the illumination and distraction from light bulbs, televisions or computers, the subjects slept through the night, at least at first. But, after a while, Dr. Wehr noticed that subjects began to wake up a little after midnight, lie awake for a couple of hours, and then drift back to sleep again, in the same pattern of segmented sleep that Professor Ekirch saw referenced in historical records and early works of literature.
It seemed that, given a chance to be free of modern life, the body would naturally settle into a split sleep schedule. Subjects grew to like experiencing nighttime in a new way. Once they broke their conception of what form sleep should come in, they looked forward to the time in the middle of the night as a chance for deep thinking of all kinds, whether in the form of self-reflection, getting a jump on the next day or amorous activity. Most of us, however, do not treat middle-of-the-night awakenings as a sign of a normal, functioning brain.