More than one-third of American adults wake up in the middle of the night on a regular basis. Of those who experience “nocturnal awakenings,” nearly half are unable to fall back asleep right away. Doctors frequently diagnose this condition as a sleep disorder called “middle-of-the-night insomnia,” and prescribe medication to treat it.
Mounting evidence suggests, however, that nocturnal awakenings aren’t abnormal at all; they are the natural rhythm that your body gravitates toward. According to historians and psychiatrists alike, it is the compressed, continuous eight-hour sleep routine to which everyone aspires today that is unprecedented in human history. We’ve been sleeping all wrong lately — so if you have “insomnia,” you may actually be doing things right.
“The dominant pattern of sleep, arguably since time immemorial, was biphasic,” Roger Ekirch, a sleep historian at Virginia Tech University and author of “At Day’s Close: Night in Times Past” (Norton 2005), told Life’s Little Mysteries, a sister site to LiveScience. “Humans slept in two four-hour blocks, which were separated by a period of wakefulness in the middle of the night lasting an hour or more. During this time some might stay in bed, pray, think about their dreams, or talk with their spouses. Others might get up and do tasks or even visit neighbors before going back to sleep.”
References to “first sleep” or “deep sleep” and “second sleep” or “morning sleep” abound in legal depositions, literature and other archival documents from pre-Industrial European times. Gradually, though, during the 19th century, “language changed and references to segmented sleep fell away,” said Ekirch. “Now people call it insomnia.”
Ekirch explained that in the past, and especially during winter, darkness spanned up to 14 hours each night. Except for those affluent enough to burn candles for hours, folks were left with little to do but go to bed early, and this gave a great deal of flexibility to their nightly sleep requirements. Segmented or biphasic sleep patterns evolved to fill the long stretch of nighttime, and as observed by anthropologists, segmented sleep continues to be the norm for many people in undeveloped parts of the world, such as the Tiv group in Central Nigeria.
In places with electricity, though, artificial lighting has prolonged our experience of daylight, allowing us to be productive for longer. At the same time, it has cut nighttime short, and so to get enough sleep we now have to do it all in one go. Now, “normal” sleep requires forgoing the periods of wakefulness that used to break up the night; we simply don’t have time for a midnight chat with the neighbor any longer. “But people with particularly strong circadian rhythms continue to [wake up in the night],” said Ekirch.
In the 1990s, a sleep scientist named Thomas Wehr discovered that everyone sleeps biphasically when subjected to natural patterns of light and dark. In Wehr’s well-known study, he subjected participants to 14 hours of darkness per night, and found that they gradually shifted to a routine of taking two hours to fall asleep, then sleeping in two four-hour phases separated by about an hour of wakefulness—a pattern that exactly matched Ekirch’s historical findings.
- Sleepless Nights- Why Do You Toss And Turn In Bed? (dangerouslee.biz)