This New Study Questions What We Thought We Knew About Sleep Eight hours of sleep may have never been the norm.
By Laura Entis
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It's a wonderful time to be alive. We have electricity. We have antibiotics. We have caramel espresso ice-cream.
One thing we don't have? Enough sleep. That we are a chronically sleep deprived nation -- run haggard by our overbooked schedules and addiction to blue-lit screens – is old news at this point. One theory is that to combat insomnia and achieve that magical 8 hours a night, we simply need to return to our ancestral roots.
According to new research, we may need to rethink this assumption. Our ancestors likely didn't get anywhere close to eight hours a night and remained awake long after the sun had set, finds a study published today in Current Biology.
To approximate our ancestor's sleeping patterns the researchers, using wearable devices, temperature recorders and in-person interviews, observed the sleeping behavior of three preindustrial societies: the Hazda of Tanzania, the San of Namibia and the Tsimane of Bolivia. Altogether, the researchers collected the sleep records of 94 adults for a total of 1,165 days, finding that members of all three tribes slept, on average, slightly less than 6.5 hours a night.
Related: How Much Sleep Do You Really Need?
This didn't come as a huge surprise to Jerome Siegel, the leader of the research team and a professor of psychiatry at UCLA's Semel Institute of Neuroscience and Human Behavior. "To be honest, I was skeptical of the claim that sleep has greatly decreased in our society," he said. It's a human impulse to romanticize the past (sleeping habits included), and apparently we've been at it for years. "A colleague of mine found a quote in an 1890 journal of medicine that said 'modern medicine is reducing sleep,'" he said. "It's easy to complain, but you need the actual numbers to bed sure about what's happening."
In addition to the lack of an eight-hour sleep cycle, Siegel's research implies that our ancestors weren't sleeping when the sun set, as is sometimes assumed. In fact, on average, members went to bed a full 3.5 hours after nightfall. While Siegel doesn't doubt that artificial light from electricity and electronics "further prolongs waking," making it more difficult for us to doze off once we hit the pillow, his research suggests the answer to our modern-day sleep woes isn't necessarily going to be earlier. Or, as fellow-researcher Gandhi Yetish put it in the study's corresponding press release, "I feel a lot less insecure about my own sleep habits after having found the trends we see here."
Another interesting aspect for Siegel was the realization that in all three societies, sleep cycles were closely synced to temperature: Sleep onset occurred as it began to get colder, and wake times tightly coincided with the coldest point in a 24-hour period, just as temperatures began to rise. By following this cycle, tribe members maintained fairly consistent wake-up times.
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Modern society, with its temperature controlled bedrooms, doesn't preserve this nightly pattern. "Humans are unique in having removed that cycle from their lives," says Siegel, and he speculates that this lack of temperature variation could be just as big as an insomnia-driver as artificial light.
With that in mind, is it possible to recreate a temperature cycle in our industrial homes? From a technology perspective "it's not a challenge" (just buy a timed thermostat) but Siegel isn't convinced that, having acclimated to controlled temperatures since birth, we'd necessarily reap the same benefits. It's an area he'd like to study in future.
All in all, Siegel hopes this study will give us pause when it comes to defining a good night's sleep. "It's dangerous for people to believe that we used to sleep 2 or 3 hours more than we do now," he says, particularly if this drives up the use of sleep pills, which have been found to do little to increase the duration of sleep while shortening average life-spans.
"Under ideal conditions people should go to sleep when they're tired and wake up regularly but without an alarm clock," says Siegel, who has been studying sleep for 40 years. "If you do this and still only get 6 hours of sleep a night, there is no reason to worry."
