12/18/12 - we used to sleep twice each night

In today's selection -- for most of history people have had two periods of sleep each night, with the time in between being perhaps the most calm and relaxing part of their lives. Then came the lightbulb. This unexpected "two sleep" phenomenon was uncovered by historian Roger Ekirch when he began to do research for a history of the night:

"Something puzzled [Roger] Ekirch as he leafed through parch­ments ranging from property records to primers on how to spot a ghost. He kept noticing strange references to sleep. In the Canterbury Tales, for instance, one of the characters in 'The Squire's Tale' wakes up in the early morning following her 'first sleep' and then goes back to bed. A fifteenth-century medical book, meanwhile, advised readers to spend the 'first sleep' on the right side and after that to lie on their left. And a scholar in England wrote that the time between the 'first sleep" and the 'second sleep' was the best time for serious study. Mentions of these two separate types of sleep came one after another, until Ekirch could no longer brush them aside as a curiosity. Sleep, he pieced together, wasn't always the one long block that we con­sider it today.

"From his cocoon of books in Virginia, Ekirch somehow rediscovered a fact of life that was once as common as eating breakfast. Every night, people fell asleep not long after the sun went down and stayed that way until sometime after midnight. This was the first sleep that kept popping up in the old tales. Once a person woke up, he or she would stay that way for an hour or so before going back to sleep until morning -- the so-called second sleep. The time between the two bouts of sleep was a natural and expected part of the night and, depending on your needs, was spent praying, reading, contemplating your dreams, urinating, or having sex. The last one was per­haps the most popular. One sixteenth-century French phy­sician concluded that laborers were able to conceive several children because they waited until after the first sleep, when their energy was replenished, to make love. Their wives liked it more, too, he said. The first sleep let men 'do it better' and women 'have more enjoyment.' ...

"About three hun­dred miles away, a psychiatrist was noticing something odd in a research experiment. Thomas Wehr, who worked for the National Institute of Mental Health in Bethesda, Maryland, was struck by the idea that the ubiquitous artificial light we see every day could have some unknown effect on our sleep habits. On a whim, he deprived subjects of artificial light for up to four­teen hours a day in hopes of re-creating the lighting conditions common to early humans. Without lightbulbs, televisions, or street lamps, the subjects in his study initially did little more at night than sleep. They spent the first few weeks of the experi­ment like kids in a candy store, making up for all of the lost sleep that had accumulated from staying out late at night or showing up at work early in the morning. After a few weeks, the subjects were better rested than perhaps at any other time in their lives.

"That was when the experiment took a strange turn. Soon, the subjects began to stir a little after midnight, lie awake in bed for an hour or so, and then fall back asleep again. It was the same sort of segmented sleep that Ekirch found in the historical records. While sequestered from artificial light, subjects were shedding the sleep habits they had formed over a lifetime. It was as if their bodies were exercising a muscle they never knew they had. The experiment revealed the innate wiring in the brain, unearthed only after the body was sheltered from modern life. Not long after Wehr published a paper about the study, Ekirch contacted him and revealed his own research findings.

"Wehr soon decided to investigate further. Once again, he blocked subjects from exposure to artificial light. This time, however, he drew some of their blood during the night to see whether there was anything more to the period between the first and second sleep than an opportunity for feudal peasants to have good sex. The results showed that the hour humans once spent awake in the middle of the night was probably the most relaxing block of time their lives. Chemically, the body was in a state equivalent to what you might feel after spending a day at a spa. During the time between the two sleeps, the sub­jects' brains pumped out higher levels of prolactin, a hormone that helps reduce stress and is responsible for the relaxed feel­ing after an orgasm. ... The subjects in Wehr's study described the time between the two halves of sleep as close to a period of meditation.

"Numerous other studies have shown that splitting sleep into two roughly equal halves is something that our bodies will do if we give them a chance. In places of the world where there isn't artificial light -- and all the things that go with it, like computers, movies, and bad reality TV shows -- people still sleep this way. In the mid-1960s, anthropologists studying the Tiv culture in central Nigeria found that group members not only practiced segmented sleep, but also used roughly the same terms of first sleep and second sleep. ... [Yet] almost two decades after Wehr's study was published in a medical journal, many sleep researchers -- not to mention your average physician -- have never heard of it. When patients complain about waking up at roughly the same time in the middle of the night, many physicians will reach for a pen and write a prescription for a sleeping pill, not realizing that they are medicating a condition that was considered normal for thousands of years. Patients, meanwhile, see waking up as a sign that something is wrong."


David K. Randall


Dreamland: Adventures in the Strange Science of Sleep


W.W. Norton & Company


Copyright 2012 by David K. Randall


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