What Can The Evolution Of Our Sleep Habits Teach Us?

When Amy Osborne started experiencing insomnia last August, it wasn't due to anything drastic. She recalls a heat wave in the Boston area where she lives, a bit more stress at work, and her schedule being thrown off for a few consecutive days. But the combination was enough to trigger a pattern: Osborne started having trouble falling asleep, and before long the problem snowballed into a chronic issue. Sometimes it would take her hours to fall asleep, or she'd wake up in the middle of the night and struggle to conk out again. Sleep -- and the lack of it -- took over her life.

"It was all I thought about during the day," she says. "I was miserable."

Osbourne tried everything she could think of to fix the problem, from transcendental meditation to acupuncture, but to no avail. Finally, she sought help from her primary care physician, who went on to prescribe a series of sleeping pills -- none of which seemed quite right. Even if Osbourne got enough sleep, the pills made her groggy the next day. Other meds made her anxious and depressed, or stopped working over time, which meant trying yet another medication. All the while, she felt the pressure to get eight straight hours, obsessing over her inability to do so.

Americans’ complicated relationship with sleep is no secret. According to the CDC, about 9 million of us use prescription sleep aids. But mainstream sleeping hours could be partly to blame. That eight-hour golden rule we all strive for? It just might be wrong. Think about it: People live in wildly different ways, and yet insist on conforming to the same sleep routine. It’s no wonder that so many of us can’t seem to win at sleep.

“One historian has identified nearly 500 historical references to biphasic or “segmented” sleep.”

But don’t hide under the covers just yet, because there could be a better approach. It’s worth taking a look back at the work of sleep researcher Thomas A. Wehr, who subjected people to 14 hours of daily darkness for a month in the 1990s. And you thought the end of daylight saving time was harsh!

As Wehr’s study progressed, something odd happened. Instead of sleeping for several hours straight, subjects began sleeping in two blocks, each about four to five hours long. In between, they lay peacefully awake for up to a few hours -- not quite what most of us experience these days when we jolt awake at 2 a.m. Follow-up research revealed why: Extended darkness triggered a release of the calming hormone prolactin and the sleep regulator melatonin; the perfect marriage for a meditative middle-of-the-night state.

What Wehr had “discovered” -- the so-called biphasic pattern of sleep -- was actually nothing new or revolutionary. As far back as 800 B.C., humans slept in two separate spans of time, between which wakefulness was considered perfectly normal. History is no stranger to segmented sleep: it’s relevant everywhere from The Odyssey to 16th-century prayer manuals. In fact, one historian has identified nearly 500 historical references to biphasic or “segmented” sleep.

It all chips away at our notion of what a night’s sleep should look like -- and even whether a “natural” human sleep pattern actually exists. Is biphasic sleep our "default" sleep setting? And, if so, how did we arrive at today's standard of one uninterrupted stretch of nightly sack time? We partnered with Sleep Number to find out more -- and explore the history, and future, of one of the most important aspects of our lives.

Sleep Habits Evolved As Humans Did: A Timeline

To better understand the way we sleep now and why, it’s helpful to look back -- way, way back. It turns out that our primate ancestors just might have kept pace with us, if only they’d gotten better sleep.

“We’re the shortest-sleeping primate,” says Charles L. Nunn, a professor of evolutionary anthropology and global health at Duke University. And our abbreviated slumber played a big role in evolution, boosting our cognitive capacities and propelling us ahead of other species. The finding comes from Nunn’s recent study, co-authored with Duke evolutionary biologist David R. Samson and titled “Sleep intensity and the evolution of human cognition.”

It all started a few million years ago, when humans began sleeping more deeply and likely with higher proportions of REM -- the rapid eye movement phase of sleep, which is key to memory and learning -- than our fellow primates did. In other words, our sleep became more efficient. Take that, primates.

Why Did Segmented Sleep End? You Can Thank Your Mattress

As for how the majority of us traded biphasic sleep for a tidy single segment, it might have something to do with beds, the Duke research suggests. A crucial shift happened about 1.8 million year ago, when humans moved their beds from the trees to the ground, eventually sleeping in groups around roaring fires. The benefits were threefold: safety in numbers, extra warmth, and juiced-up REM periods, courtesy of our more relaxed and stable bodies.

“We have better things to do than sleep. That's not a modern creation, even though it seems to be treated that way.”

- Charles L. Nunn, Duke University

We got so good at sleep that we simply didn’t need as much. And when we began sleeping better and less, we left our primate ancestors in the cognitive dust. Early humans suddenly had more time to learn from each other -- things like new hunting and cooking techniques and where to find food. Other primates? They couldn’t keep up. But humans kept pushing to acquire more new skills and knowledge.

We have better things to do than sleep,” says Nunn. “That's not a modern creation, even though it seems to be treated that way.

And With Cognitive Progress Came Scientific Studies

The smarter we got, the more we wanted to know about sleep. The ancient Greeks kicked things off with a slew of theories, starting between 500 and 450 B.C. when philosopher and physician Alcmaeon equated sleep with losing consciousness. Later, in 350 B.C., Aristotle contended that sleep helped digestion and physical growth and renewed the heart.

Today, we still tend to think of sleep in physical terms -- a way to restore the body or recover from fatigue. But that can be to our detriment; we often overlook the fact that sleep affects how we feel and think.

Meanwhile, research shows that our most important thought processes depend on good sleep, from emotional regulation and social acuity to decision-making and moral reasoning. Miss out on sleep and you run the risk of losing your cool at work, fumbling in personal relationships and making haphazard choices. No big deal, right?

And Then, There Were Sleeping Pills: Sleep Habits In The Modern Age

Unfortunately, our flimsy grasp of the importance of sleep only intensified with the industrial revolution in the 18th and 19th centuries. People left small farms for urban centers. Long workdays, strict schedules and intensive physical labor became the norm. So did exhaustion.

“We don't respect sleep or circadian rhythms enough. It hasn't caught on in our culture yet.”

- Dr. Deirdre A. Conroy, University of Michigan

Human sleep took a turn. People were so tired that they started sleeping in consolidated seven- to eight-hour chunks, says Matthew J. Wolf-Meyer, associate professor of anthropology at Binghamton University and the author of The Slumbering Masses: Sleep, Medicine and Modern American Life. But those inflexible sleep standards didn’t work for everybody.

And they still don’t necessarily work, says Dr. Deirdre A. Conroy, clinical associate professor and clinical director of behavioral sleep medicine at the University of Michigan Department of Psychiatry. Some of Conroy’s patients have delayed sleep cycles -- they’d be better off sleeping from, say, 2 a.m. until 10 a.m. -- but inflexible workplaces make doing so impossible, and can leave people in a constant state of sleep deprivation.

We don't respect sleep or circadian rhythms enough. It hasn't caught on in our culture yet,” Conroy says.

You can blame the rise of modern sleep medicine in the 1920s for that. Researchers relied on static industrial-era ideas for the picture of sleep normalcy, says Wolf-Meyer. Instead of exploring other possible sleep models, doctors began correcting unconventional sleep patterns -- which people saw as a threat to productivity -- with medicine.

Our modern-day reliance on sleep aids seems unsurprising in retrospect. The mindset that there’s only one way to sleep -- at night, without any interruptions, for eight hours -- is the very attitude that leads people to cheat the system.

A Slippery Slope: Downplaying The Importance Of Sleep

The pressure we feel to medicate ourselves to adhere to sleeping norms may even come from up high; some influential figures have publicly downplayed the need for sleep, even denigrating it entirely.

Thomas Edison famously called sleep “a heritage from our cave days” and reportedly only slept three or four hours a night. This kind of thinking can be infectious and has persisted for decades. Numerous high achievers in recent years have upheld their eschewing of a solid night’s rest as a point of pride.

Morning show host Willie Geist apparently tricks his body into feeling well-rested after just four hours of sleep. Media mogul Martha Stewart has admitted to neglecting Zs. Twitter CEO Jack Dorsey? Four to six hours a night suits him just fine. And, before heart and lung surgeries slowed him down, President Bill Clinton only slept five hours a night.

Way to make the rest of us feel inferior, guys.

Finally: How We Think About Sleep Today

Some of our unhealthy notions of sleep do seem to be unraveling. Oft-cited 2002 research revealed a vital link between sleep and longevity: People who sleep seven hours a night live longer than those who sleep eight or more hours, or six or fewer hours.

That message is even sinking in among bastions of notoriously bad sleep habits, such as the corporate world. CEOs and CFOs are hiring sleep coaches to get their habits back on track, and signing on for MIT neuroscientist Tara Swart’s courses on sleep and mindfulness training. Holistic approaches to sleep that integrate nutrition and overall wellness, such as Conroy’s private practice, Happy Healthy Rested, are also catching on outside of the corporate realm.

“Since tapering off of the meds, and adopting a schedule of limited time in bed every day, Ozski has started falling asleep within a half-hour of lying down most nights.”

As for Amy Ozski, she shifted her approach last December. Having tried several different ineffective prescription sleep aids, Ozski took the advice of her primary care doctor and started cognitive behavioral therapy (CBT) for insomnia with Dr. Suzanne Bertisch at Beth Israel Deaconess Medical Center, Harvard Medical School Teaching Hospital. A growing body of research backs up CBT, which tackles negative beliefs and habits surrounding sleep. Since tapering off of the meds, and adopting a schedule of limited time in bed every day, Ozski has started falling asleep within a half-hour of lying down most nights. Middle-of-the-night waking happens less frequently, and she only takes a low dose of a prescription sleep aid when she absolutely has to.

“I didn’t want to be on pills for the rest of my life,” Ozski says. “I’m just glad that I’m alive at a time when [CBT is] something that people are studying.”

Looking To The Future: How We’ll Sleep Tomorrow

Today, we have a broad understanding of the important impact sleep has on different aspects of health. We understand that there’s not one right way to sleep now, nor has there ever been; cultural and biological differences come into play. “The number of hours of sleep that someone needs is highly individual,” says Conroy. The question is what we’ll do with our heightened grasp of that mysterious third of our lives.

Thanks to technology, some of us have become our very own sleep scientists. Wearable sleep trackers can detect everything from REM sleep to cardiopulmonary patterns associated with obstructive sleep apnea. Sophisticated napping pods are making public sleeping possible, even at the office, allowing for a variety of sleep patterns and schedules to coexist. Down the road, researchers could create technology that allows us to pack more sleep into even fewer hours.

Whether our approach is high-tech or mindful, or rooted in behavioral therapy, we are starting to recognize that sleep habits are key not only to our longevity, but also to maximizing the years we have. Just as our ancestors evolved their sleeping practices to give us a leg up on other species, today we continue that evolution in the pursuit of a more perfect slumber.

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