It's a standard doctor's query: Are you getting your full eight hours of sleep at night? Well, if you find yourself staring at the ceiling at about 2 a.m. (and worrying about what is keeping you up), here's some reassuring news: Your body clock may have it right.
Exploring some of the historic trends and research on sleep, BBC magazine article suggests that the typically human pattern of shut-eye isn't actually eight uninterrupted hours – but two sets of four hours instead.
The magazine cites research, including a paper by historian Roger Ekirch at Virginia Tech, who after 16 years of study found a bundle of evidence – in diaries, court documents and literature – that humans naturally used to divide their sleep in two, often waking up in the middle for a couple hours.
In the middle wake-up, Dr. Ekirch reports, people might stay in bed, read or write, go out and visit neighbours, or even partake in some middle-of-the-night canoodling. (The research uncovered a doctor's manual from 16th-century France that recommended couples trying to conceive had the best chance between after the "first sleep," as it was called.)
In the 19th century, the notion of the first and second sleep began to lose favour, and by the 1920s, the pattern had pretty much vanished – snuffed out with the advent of street lighting and a surge of coffee houses, and as the amount of time people had available for lying around in bed either sleeping, or in between, shortened.
But Dr. Ekirch's argument, as the BBC explains, is that while most people have adapted to one long sleep, many sleep problems may be attributed to going against the natural preference for sleeping in segments.
The historian also found support from some sleep scientists, including Russell Foster, a circadian neuroscientist at the University of Oxford. "Many people wake up at night and panic," he told the BBC. "I tell them that what they are experiencing is a throwback to the bi-model sleep pattern."
Of course, this research falls amid all sorts of studies warning of the health risks of sleeping too little or too much. But another new study this month, which looked at how well adolescents fared on tests after a certain amount of sleep, found that the optimal time 16-year-old is about seven hours. (For 10-year-olds, it was about 9.5 hours, for 12-years-old about 8.5 hours.)
What to take away from this two-sleeps research? If you wake up at about 2 a.m. with an urge to do the laundry or buy your groceries or perhaps some friskier activity, have at it. Presumably, you're just following in the footsteps of your soundly sleeping ancestors. But here's hoping you get that second sleep in before the alarm clock goes off.
Do you have trouble sleeping, or do you get a full night's rest? Are you worried about your sleeping patterns?