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Chapter 1

I Know What You Did Last Night

One night, not long ago, a man found himself collapsed in a hallway, clutching his leg like a wounded bear. As his curses and howls echoed through the walls of his apartment on an otherwise silent Tuesday night, a thought passed across his brain: something had gone wrong. It was after midnight. He was not supposed to be in this position, on his back on a hardwood floor, and he was definitely not supposed to be in this much pain. He lay there, hurt and confused, not knowing what had happened, since his last memory was laying his head down on a pillow in the bedroom thirty feet away.

That man was me. It had never occurred to me, before that moment, that falling asleep could lead to injury. But there I was, in my boxers, piecing together the last few hours of my life like a disheveled detective who came late to a crime scene. Three things were immediately clear: 1) I had crashed into a wall in my apartment while sleepwalking; 2) I don't sleepwalk with my arms out in front of me like a zombie, which is a pity because 3) sleepwalking into a wall really hurts.

This was the first time that I sleepwalked, or at least the first time that I did it so badly that I ran into something. But sleep had long been a less-than-peaceful part of my life. As a child, I often fell asleep with my eyes open, a condition that unnerved my parents and spooked friends at sleepovers. When I was in college, I unknowingly entertained my roommates while I was sleeping by sitting up and yelling things like "Man the barricades, the bacon is coming!" Now, as a married adult, my wife is treated to a nightly show that can include talking, singing, laughing, humming, giggling, grunting, bouncing, and kicking. She handles all of this by putting in earplugs after we say good night and moving to the far side of our oversized bed, a purchase she insisted on after being on the receiving end of one well-placed kick.

The talking and kicking she could deal with. But she put her foot down once I became mobile. After a few days of limping around and hoping no one would ask why, I found myself in a sleep lab at a New York hospital. The room was decorated like a hotel room in Florida, complete with a pink watercolor painting of a palm tree hanging above what at first glance looked like a headboard. A deeper inspection revealed that it was a piece of wood bolted to the wall above a standard-issue hospital bed. The walls were painted cream, and one of the last working television-VCR combinations sat on top of a desk in the corner. Medical equipment shared space with a white beach shell on a wooden nightstand.

My brain waves were to be recorded as I slept that night so that a neurologist could see what was going on. To round the picture out, my heartbeat, breathing rate, limb movements, body temperature, and jaw pressure would be captured as well. Cue the electrodes, sixteen in all, attached to sites ranging from my temples to my ankles. A technician slathered each spot on my head with sticky white goo, manipulating my hair into what could be called the Contemporary Einstein. She taped a forked monitor inside my nostrils, glued oval sensors to each of my cheeks, and bound what appeared to be a glowing red clothespin to my index finger. A plastic blue box heavy with wires running in and out of it hung around my neck. The process of putting all of this on my body took forty-five minutes. After she finished, the technician told me that she would be in a room down the hall watching me via a video camera fixed on the ceiling and pointed at the bed. "Try to sleep normally," she said as she closed the door. If she was aware of the irony, she didn't show it.

I tried to get comfortable. After a few minutes, I turned to my right side. Suddenly, a voice calling out from a pair of hidden speakers above the headboard echoed in the small room. "Sir, you cannot sleep on your side. You must stay on your back," the technician said. A blinking red light on the ceiling revealed the camera that gave me away. I lay there like a board, wondering when this would be over. That night, I dreamt that I was in a prison.

A few days later, I sat in the office of the neurologist who had ordered the study, a long, slender man whose oversized glasses made his face look too small for his body. He rustled through the more than three hundred pages of data collected from my night in the sleep lab, past charts showing my brain waves spiking and falling like a boom and bust stock market. His hands settled on the summary he was looking for. He studied it quietly for a few minutes. Finally, he spoke.

"Well, you certainly kick a lot."

I waited, hoping there was more to come from a test that set my health insurance company back a couple-thousand dollars.

"But beyond that, I'm not sure what we can do for you," he continued. "Your breathing is normal, so you don't have sleep apnea. You're not having seizures in your sleep. You awaken easily, that's clear, but that's not really a medical problem. I could give you a sleeping pill, but frankly I'm not sure that it's going to help."

"Do I have restless leg syndrome?" I asked, suddenly feeling like an actor in one of those commercials that tell you to ask your doctor whether a medication is right for you.

"Do your legs feel uncomfortable if you don't kick them?"

"Not really," I replied.

"Then it's not restless leg. It may be a mild case of periodic limb movement disorder, but there's not much we can do for that."

I liked the sound of the word mild. "So what should I do?" I asked.

"I'm going to be honest with you. There's a lot that we know about sleep, but there's a lot we don't know. If the sleepwalking continues, let's try some sedatives. But I don't want you to start taking drugs that you don't need. Try to cut down on your stress and see what happens."

I left the appointment with the vague feeling that I had been tricked. I expected science to have as thorough an understanding of sleep as it does of digestion, or any other bodily function that we can't live without. Instead I heard a doctor's disconcerting admission that he didn't know what was going on or how to stop it. It was as if my body had sleepwalked itself past the frontier.

Sleep wasn't something that we were supposed to worry about in the first years of the twenty-first century. There were bigger issues requiring attention. Technology was making the world smaller by the day, the global economy blurred the lines between one day and the next, and daily life was filled with questions over what was considered normal. Many people never gave sleep much thought, and if they did, considered it nothing more than an elegant on/off switch that the body flips when it needs to take a break from its overscheduled life. Sure, we would probably like to get more of it, and yes, we may have had a weird dream or two lately, but beyond that, the importance of sleep likely hovers somewhere near that of flossing in most of our lives: something we are supposed to do more often but don't.

Most of us will spend a full third of our lives asleep, and yet we don't have the faintest idea of what it does for our bodies and our brains. Research labs offer surprisingly few answers. Sleep is one of the dirty little secrets of science. My neurologist wasn't kidding when he said there was a lot that we don't know about sleep, starting with the most obvious question of all—why we, and every other animal, need to sleep in the first place.

Consider, for a moment, how absurd the whole idea of falling asleep is in a world of finite resources where living things resort to eating each other to survive. A sleeping animal must lie still for long stretches at a time, all but inviting predators to make it dinner (and not in a good way). Yet whatever sleep does is so important that evolution goes out of its way to make it possible. A dolphin, for instance, will sleep with half of its brain awake at a time, giving it the ability to surface for air and be on the lookout for predators while the other half is presumably dreaming. Birds, too, have adapted the ability to decide whether to put half of their brain to sleep or the whole thing. Imagine a flock of ducks sleeping at the edge of a lake. The birds at the periphery of the group will likely be sleeping with one-half of their brain awake and aware of their surroundings, keeping watch while their companions in the middle zonk out completely.

You would think, then, that sleep is a luxury that increases as you move up the food chain, and that sharper claws would equal longer dreams. But no. Lions and gerbils sleep about thirteen hours a day. Tigers and squirrels nod off for about fifteen hours. At the other end of the spectrum, elephants typically sleep three and a half hours at a time, which seems lavish compared to the hour and a half of shut-eye that the average giraffe gets each night.

The need to sleep interferes with other more biologically pressing needs, such as procreating, finding and gathering food, building shelter, and anything else you might do to ensure that your genetic line lives on. Sleep is so important, yet so poorly understood, that it led one biologist to say, "If sleep doesn't serve an absolutely vital function, it is the greatest mistake evolution ever made." That function is still a mystery. It would be nice to say that sleep is nothing more than the time when a body rests, but that wouldn't be quite right either. You can relax in a hammock on a beach all day long if you want to, but after about twenty hours you will be in pretty bad shape if you don't fall asleep and stay that way for a while. Humans need roughly one hour of sleep for every two hours they are awake, and the body innately knows when this ratio becomes out of whack. Each hour of missed sleep one night will result in deeper sleep the next, until the body's sleep debt is wiped clean.

The only thing stranger than the need to sleep is what happens when it is ignored. In 1965, a San Diego high school student named Randy Gardner stayed awake continuously for 264 hours, an eleven-day feat documented by a team of researchers from Stanford University who happened to read about his attempt beforehand in the local newspaper. For the first day or so, Gardner was able to remain awake without any prompting. But things went south quickly. He soon lost the ability to add simple numbers in his head. He then became increasingly paranoid, asking those who had promised to help him stay up why they were treating him so badly. When he finally went to bed, he slept for nearly fifteen hours straight. And yet a few weeks later, he was as good as new. To this day, he continues to be a minor celebrity in Japan.

Gardner experienced a happier ending than most subjects of sleep deprivation experiments. In the 1980s, researchers at the University of Chicago decided to find out what happens when an animal is deprived of sleep for a long period of time. In but one of the many odd tests you will find in the history of sleep research, these scientists forced rats to stay awake by placing them on a tiny platform suspended over cold water. The platform was balanced so that it would remain level only if a rat kept moving. If a rat fell asleep, it would tumble into the water and be forced to swim back to safety (or drown, an option that the researchers seemed strangely blasé about).

Fast-forward to two weeks later. All of the rats were dead. This confused the researchers, though they had a few hints that something bad was going to happen. As the rats went longer and longer without sleep, their bodies began to self-destruct. They developed strange spots and festering sores that didn't heal, their fur started to fall out in large clumps, and they lost weight no matter how much food they ate. So the researchers decided to perform autopsies, and lo and behold they found nothing wrong with the animals' organs that would lead them to failing so suddenly. This mystery gnawed at scientists so much that twenty years later, another team decided to do the exact same experiment, but with better instruments. This time, they thought, they will find out what happens inside of a rat's body during sleep deprivation that ultimately leads to its death. Again the rats stayed awake for more than two weeks, and again they died after developing gnarly sores. But just like their peers in Chicago years earlier, the research team could find no clear reason why the rats were keeling over. The lack of sleep itself looked to be the killer. The best guess was that staying awake for so long drained the animal's system and made it lose the ability to regulate its body temperature.

Humans who are kept awake for too long start to show some of the same signs as those hapless rats. For obvious reasons, no one has conducted any scientific research into whether it is possible for a person to die from extreme sleep deprivation. The closest we have come are short-term sleep deprivation studies conducted by the government, with subjects participating voluntarily or not. CIA interrogators at Guantánamo Bay, for instance, subjected dozens of enemy combatants to sleep deprivation by chaining them together and forcing them to stand for more than a day at a time. Justice Department officials later wrote in a memo that "surprisingly, little seemed to go wrong with the subjects physically."

Signs that the lack of sleep was affecting their bodies were most likely there but not apparent to the naked eye. Within the first twenty-four hours of sleep deprivation, the blood pressure starts to increase. Not long afterward, the metabolism levels go haywire, giving a person an uncontrollable craving for carbohydrates. The body temperature drops and the immune system gets weaker. If this goes on for too long, there is a good chance that the mind will turn against itself, making a person experience visions and hear phantom sounds akin to a bad acid trip. At the same time, the ability to make simple decisions or recall obvious facts drops off severely. It is a bizarre downward spiral that is all the more peculiar because it can be stopped completely, and all of its effects will vanish, simply by sleeping for a couple of hours.

I know all of this only because I walked out of that neurologist's office with more questions than answers. As I headed home, wondering if I would sleepwalk again and how badly it would hurt if I ran into something the next time, my confusion gave way to a plan. If my doctor couldn't tell me more about sleep, I reasoned, then I would go out and search for the solutions myself. A third of my life was passing by, unexamined and unaccounted for, and yet it was shrouded in mystery.

So began my adventures in the strange science of sleep. I set out to discover everything I could about a period of time that we can only conceive of as an abstraction, a bodily state that we know about but never really experience because, well, we are asleep. Once I started really thinking about sleep for the first time, the questions came in waves. Do men sleep differently than women? Why do we dream? Why is getting children to fall asleep one of the hardest parts of becoming a new parent, and is it this hard for everyone around the world? How come some people snore and others don't? And what makes my body start sleepwalking, and why can't I tell it to stop? Asking friends and family about sleep elicited a long string of "I don't knows," followed by looks of consternation, like the expressions you see on students who don't know the answers to a pop quiz. Sleep, the universal element of our lives, was the great unknown. And frankly, that makes no sense.

Despite taking up so much of life, sleep is one of the youngest fields of science. Until the middle of the twentieth century, scientists thought that sleep was an unchanging condition during which time the brain was quiet. The discovery of rapid eye movements in the 1950s upended that. Researchers then realized that sleep is made up of five distinct stages that the body cycles through over roughly ninety-minute periods. The first is so light that if you wake up from it, you might not realize that you have been sleeping. The second is marked by the appearance of sleep-specific brain waves that last only a few seconds at a time. If you reach this point in the cycle, you will know you have been sleeping when you wake up. This stage marks the last stop before your brain takes a long ride away from consciousness. Stages three and four are considered deep sleep. In three, the brain sends out long, rhythmic bursts called delta waves. Stage four is known as slow-wave sleep for the speed of its accompanying brain waves. The deepest form of sleep, this is the farthest that your brain travels from conscious thought. If you are woken up while in stage four, you will be disoriented, unable to answer basic questions, and want nothing more than to go back to sleep, a condition that researchers call sleep drunkenness. The final stage is REM sleep, so named because of the rapid movements of your eyes dancing against your eyelids. In this type of sleep, the brain is as active as it is when it is awake. This is when most dreams occur.

Your body prepares for REM sleep by sending out hormones to effectively paralyze itself so that your arms and legs don't act out the storyline you are creating in your head. This attempt at self-protection doesn't always work perfectly, and when that happens, what follows is far from pleasant. Sometimes, it is the brain that doesn't get the message. This can lead to waking up in the middle of the night with the frightening sensation that you can't move your limbs. In the Middle Ages, this was thought to be a sign that a demon called an incubus was perched on the chest. Instead, this condition is simply a flaw in the sleep cycle, a wrong-footed step in the choreography of the brain's functions that allows a person to become conscious when the body thinks the brain is still dreaming. At other times, the body doesn't fully paralyze itself like it is supposed to. This is the root of a series of problems called parasomnias, of which sleepwalking like mine is by far the most mild. Patients with REM sleep disorder, for instance, sometimes jump out of a window or tackle their nightstand while they are acting out a dream. Some patients I spoke with who have this disorder have resorted to literally tying themselves to the bedpost each night out of the fear that they will accidentally commit suicide.

Before the discovery of rapid eye movements, our understanding of sleep hadn't undergone any dramatic revisions in more than two thousand years. The Ancient Greeks believed that someone fell asleep when the brain became filled with blood, and then woke up once it drained back out again. Beyond that, they found the whole experience kind of spooky. Sleep was considered the closest a living being could come to death and still be around to talk about it afterward. The immortal family tree made this clear: Hypnos, the Greek god of sleep, was the twin brother of Thanatos, the god of death, and their mother was the goddess of night. It was probably best not to think about this too much while lying in a room on a dark and lonesome evening. Two-dozen centuries later, doctors put forth the theory that blood flowing through the head put pressure on the brain and induced sleep, a concept Plato would have readily agreed with. Philosophers in the nineteenth century introduced the novel idea that a person fell asleep when the brain ceased to be filled with stimulating thoughts or ambitions. The supposed link between sleep and an empty head fostered a suspicion of anyone who slept too much or seemed to enjoy it. In certain high-pressure jobs today, admitting that you sleep for more than five or six hours each night still looks to be a sure sign that you are not a serious person.

Whether any of us has a sleep problem or not, it is clear that we are living in an age when sleep is more comfortable than ever and yet more elusive. Even the worst dorm-room mattress in America is luxurious compared to sleeping arrangements that were common not that long ago. During the Victorian era, for instance, laborers living in workhouses slept sitting on benches, with their arms dangling over a taut rope in front of them. They paid for this privilege, implying that it was better than the alternatives. Families up to the time of the Industrial Revolution engaged in the nightly ritual of checking for rats and mites burrowing in the one shared bedroom. Modernity brought about a drastic improvement in living standards, but with it came electric lights, television, and other kinds of entertainment that have thrown our sleep patterns into chaos.

Work has morphed into a twenty-four-hour fact of life, bringing its own set of standards and expectations when it comes to sleep. As the Wall Street banker who follows investments simultaneously in Dubai, Tokyo, and London knows, if you aren't keeping up, you risk being left behind. Sleep is ingrained in our cultural ethos as something that can be put off, dosed with coffee, or ignored. And yet maintaining a healthy sleep schedule is now thought of as one of the best forms of preventative medicine.

Stanford University, one of the world's premier centers of sleep research, established the first university laboratory center devoted to treating sleep disorders in 1970. The opening of Stanford's clinic started a revolution in the way the medical field approached sleep. Until then, most doctors thought that their responsibility ended once a patient nodded off each night. By 2011 there were over seventy-five recognized sleep disorders, and the number continues to grow. Some, like sleep apnea, are so common that if they aren't present in your bedroom, there is a very good chance you will find them next door. Others are simply baffling. One rare type of prion disease called fatal familiar insomnia strikes after a person reaches the age of forty. This genetic disease has been found in only a handful of families around the world. Its chief symptom is the gradual inability to fall asleep. Within a year of the first signs of the condition, patients typically die after suffering through months of agony, beset by chronic migraines and exhaustion. Their minds remain clear and unaffected until death.

There is more to sleep than medical curiosities, however. This is a book about the largest overlooked part of your life and how it affects you even if you don't have a sleep problem that sends you into a wall in the middle of the night. I began my research into sleep with the self-serving intention of finding a way to prevent future run-ins. But as I spent more time investigating the science of sleep, I began to understand that these strange hours of the night underpin nearly every moment of our lives. Police officers, truck drivers, and emergency-room physicians, for instance, are turning to sleep researchers for help in navigating sleep's effects on the brain's decision-making process. If you have ever flown on an airplane, gone to a hospital, or driven on a highway at night—or plan on doing so in the future—then you have a vested interest in how companies and organizations try to prevent costly and deadly accidents caused by something as manageable as fatigue. School districts across the country, meanwhile, have changed the time that the first bell rings in the wake of research showing that simply starting the school day later leads to significantly higher SAT scores. And new studies suggest that learning a new skill or finding a solution to a problem may simply be an outcome of the time that we spend dreaming each night.

Because of the number of new findings in such a short time span, today's researchers believe that they are in the golden age of their field. Sleep is now understood as a complex process that affects everything from the legal system to how babies are raised to how a soldier returning from war recovers from trauma. And it is also seen as a vital part of happiness. Whether you realize it or not, how you slept last night probably has a bigger impact on your life than what you decide to eat, how much money you make, or where you live. All of those things that add up to what you consider you—your creativity, emotions, health, and ability to quickly learn a new skill or devise a solution to a problem—can be seen as little more than by-products of what happens inside your brain while your head is on a pillow each night. It is part of a world that all of us enter and yet barely understand.

Sleep may not immediately come across as the most adventurous topic to investigate. After all, people who are sleeping are usually just lying there, making it very hard to interview them. What could possibly be interesting about that? My aim is to convince you otherwise by taking you on a tour of often odd, sometimes disturbing, and always fascinating things that go on in the strange world of sleep, a land where science is still in its infancy and cultural attitudes are constantly changing. I will take you through the story of a night, starting with the unrecognized forces at work in your bedroom as you fall asleep and ending with the latest research into what goes into a good night's rest.

This is not your typical advice book filled with ten easy steps to perfect sleep. But you will come away with a new understanding of all that goes on in your body while you are sleeping and what happens when you neglect sleep for too long. Hopefully, this will inform your future decisions affecting everything from your health to your wallet. You don't have to take my word for it. By the end of this book, you will have met, among others, dream researchers, professional sports trainers, marriage counselors, pediatricians, constitutional scholars, gamblers, and a university professor who investigates what could only be called sleep crime.

I never found the cure for sleepwalking that I was looking for, though I did learn what I could do to make it less likely to happen again without resorting to medication. But no matter what steps I take, or how much yoga I do to relax myself before bedtime, I very well may wake up once again in the middle of the night, disoriented and away from my bed. On the other hand, I may never sleepwalk again. That's the bizarre beauty of sleep, a seemingly simple part of life with more possible outcomes each night than you can imagine. I've been to military bases and corporate headquarters, campus labs and convention centers, all in search of what we can learn from this curious and universal fact of life if we took the time to examine it.

Sleep isn't a break from our lives. It's the missing third of the puzzle of what it means to be living.