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It appears that in centuries past, and in pre-industrial societies, bedtime has meant falling asleep once, then waking for awhile, and then going back to bed for a “second sleep.”
Bad sleepers rarely hear good news. Insomniacs often read about the latest ways our nighttime pacing is believed to be wrecking our health. Or we are treated to recycled and often unrealistic advice about how to shift around our routines to encourage sounder sleep. We can feel guilty if we find ourselves unable to follow it.

So my curiosity was piqued when a recent BBC online story, "The myth of the eight-hour sleep," shone a light on a growing body of research suggesting that "segmented sleep" is perfectly normal. It appears that in centuries past, and in pre-industrial societies, bedtime has meant falling asleep once, then waking for awhile, and then going back to bed for a "second sleep."

"That sounds like me," I thought - as many others surely did. Historians are arguing that everyone used to spend the night that way. For those who wake up in the middle of the night, this could be liberating news.

Before artificial lighting "colonized" the darkness (to borrow a term from the historian Craig Koslofsky), a nightly wakeful interlude was expected. Lighting and caffeinated beverages promoted active, chatty evenings. This, historians believe, believe pushed back the Western world's bedtime. The modern ideal of a continuous eight-hour slumber was born.

But prior to that, the idea of a "first" and "second" sleep was so routine, one researcher wrote, "it provoked little comment at the time."

This was the insight of A. Roger Ekirch, a professor of history at Virginia Tech. In his 2005 book At Day's Close, he argued that: "Until the close of the early modern era [roughly the year 1800], Western Europeans on most evenings experienced two major of sleep bridged by an hour or more of quiet wakefulness." This period was known as the "watch" or "watching."

"Segmented sleep has a lot of historical evidence," says Koslofsky, an associate professor of history at the University of Illinois and author of last fall's Evening's Empire: A History of the Night in Early Modern Europe. "[Ekirch] really demonstrated that these terms, 'first' and 'second' sleep, appeared in Homer, in Virgil, in ancient medieval Christian literature," he says. Humbler literature including diaries and prayer books also contain clues to how Westerners slept in the past.

Segmented sleep, Koslofsky says, "also seems to appear in societies that don't have a lot of access to artificial light. ... I think it's a natural feature of human evolution to break any long, dark period up into two sleeps."

Take the Trumai, an indigenous people in Brazil. They used to get up in the middle of the night to socialize and flirt by the fireside, smoke, or go fishing. The introduction of electricity to their society put an end to their midnight wanderings. Similar behaviour has been documented in other cultures.

If biphasic slumber is common, could it be the "correct" way to sleep? That is, did evolution design us for two four-hour chunks of rest? What is ideal, anyway?

"That is really the question that should be asked," says Charles Samuels, medical director of the Centre for Sleep and Human Performance in Calgary. "Establishing norms when it comes to human sleep is very difficult and complex."

It appears we do fall into a segmented sleep pattern when coffee and electricity are confiscated from us. The BBC noted a 1990s experiment by the psychiatrist Thomas Wehr, in which subjects were enveloped in profound darkness for 14 hours every night for a month. Over time, they drifted into a biphasic pattern. This was a sign, it has been suggested, that segmented sleep has a prehistoric pedigree.

Samuels is open to that possibility. But he questions whether we could make any practical use of the revelation in the 21st century.

"Could it be that we're genetically determined to sleep this way? Yes," Samuels says. However: "I think the most important thing to remember is that [in] 2012, the world does not operate the way it did. It's all well and good to say that in the past people [had biphasic sleep], but the question is, what's the relevance today? In this day and age, when people have to go to work in the morning and at home at night, we don't have a lot of choice. We really only have the nighttime to rest."

Samuels listens to a brief account of my sleep disturbances: Several times a week, I find myself waking up sometime between 2:30 and 6 a.m., and spend between at least 30 minutes - and often more than two hours - unable to get back to sleep. Is that my body trying to sleep biphasically?

Samuels thinks not. "We would call that 'maintenance insomnia.' " It's common.

Yet it's still tempting to cast aside my little pharmacopeia of herbal teas the occasional over-the-counter sleeping pill. It may be worthwhile giving the two-sleep pattern a trial run - or at least stop feeling guilty about my sleeplessness.

"You might feel relieved when you hear [historical evidence] that there's nothing wrong with that," Koslofsky says.

I do. Maybe even enough to rest a little easier.