“Put college students on four hours of sleep a night, and then give them a glucose tolerance test, and they look prediabetic. Food consumption goes up.” This is insulin resistance, provoked solely by lack of sleep. Obesity and sleep loss have long been associated, but the research has zeroed in on the reasons why. For instance, in a study published after our conversation with Stickgold, researchers based at the University of Colorado found that sleep deprivation did indeed show a marked increase in weight gain, even with no measurable decline in activity or in energy expenditure. Instead, the experience disrupted the body’s signaling pathways associated with the insulin response, particularly a set of hormones that signal satiety: ghrelin, leptin, and peptide YY. As a result, people ate more—especially women, especially in the evening.
Sick: Sleep deprivation seems to wreak havoc with the immune system, and this is not especially difficult to prove. Again, volunteers are sleep-deprived for just a few days, and then researchers give them and a control group a hepatitis C vaccination. The sleep-deprived people produce fully 50 percent fewer antibodies in response to the vaccine, a measure that says their immune systems are about half as effective.
This is what Stickgold means by subtle, in that most of us would never notice a compromised immune system, and most of us would never associate that cold with a lack of sleep.
“Is that going to kill you? Maybe. If it does, you are never going to connect the dots,” he says.
Stupid: Well, yes, and just that directly. Reams of research and a variety of related ideas demonstrate this conclusively: Sleep-deprived people generally perform more poorly on straightforward skills tests, such as the ability to recall a list of facts. Subjects allowed to nap between learning the facts and taking the recall test do better. And this area of inquiry is what has made sleep science something of a growth industry. As the Snickers bars suggested, the military paved the way, but the front of this effort now is centered in the dollars-and-cents world of business. Sleep is just good business.
For instance, companies like Google, Nike, Procter & Gamble, and Cisco Systems have begun allowing employees to take naps at work as a way to enhance both productivity and creativity. Business consulting firms have capitalized on the research to show that sleep is essential to success.
On a simple and important level, all of this is a matter of competence, of simple ability to recall facts and solve problems, and indeed the work began aimed at those sorts of skills. Stickgold, for instance, is known for running labs full of subjects playing the popular video game Tetris and demonstrating that various combinations of sleep made them better at it. This is enough to fly straight in the face of the popular archetype of our culture drawn from Silicon Valley, where, legend tells us, fortunes were made by amped-up engineers writing code around the clock, never leaving the office and never taking a break. It is a dangerous stereotype. Still, it persists, and Stickgold has a way of challenging it directly. Students he knows who still buy into this idea of the caffeinated overachiever often boast of their ability to function on four or five hours of sleep each night. He suggests to them that they account for their time and performance, and they quickly figure out that the reason they need to work twenty hours a day is they are doing everything twice. They have to, because sleep loss is making them work inefficiently.
John encounters this problem in schools, especially when he is working in Asia. Kids are extremely sleep-deprived from staying up all night playing video games. They come to school and perform poorly, then are sent to special study halls at night, lose more sleep, then play more video games, and the downward spiral continues.
In fact, the research suggests that sleep has far more effect on far more complex skills, that it almost serves as a sort of retreat for our brains, a time to shut out extraneous noise and the rush of new information and, instead, sort through information to make sense of it. Seen in this light, sleep is a time for forgetting, for putting away what is not relevant, for pruning and sorting to allow the remaining information to form patterns and assist your brain in recognizing those patterns. This helps explain the almost legendary anecdotes about creative bursts and elegant solutions to complex problems that emerged spontaneously after a good night’s sleep, the sort of thing that wins someone a Nobel Prize.
In our conversation, though, Stickgold raised a more mundane example of a common decision someone must make when offered a new and better job in a new town.
“The anal-compulsive person draws a chart: stay, go, pluses and minuses. It never helps. But then they wake up the next morning and say they can’t take the job. And when friends say ‘Why?,’ they say, ‘It’s just not right for me,’ and they can’t tell you why.”
The chart doesn’t help because it can’t include all the costs and benefits to the person and the spouse and the children and the weight of severed relationships and distance from family and the upheaval of disrupting a life. Not all of these can be neatly categorized and quantified, and even to the degree that they can, the calculation load becomes literally mind-boggling. The important judgments we make in our lives do not yield to lists of pluses and minuses and calculations. We settle these issues during sleep because that is when the brain seems best able to tackle the incalculable problems by pruning, consolidating, and synthesizing.
“One of Bob’s aphorisms,” says Stickgold, “is that for every two hours your brain spends taking in information during the day, it needs an hour of sleep to figure out what it means. If you don’t get that hour, you don’t figure it out. The difference between smart and wise is two hours more sleep a night.”
This idea takes on a new dimension in the results of further research that appears at first to be a simple test of recall. Researchers showed subjects lists of images and then tested both people who were sleep-deprived and those who weren’t on recall of the images. But these were images with clear emotional content, like a soft little puppy or an image of war, images sortable as negative, positive, or neutral emotionally. Of course, as we’ve already discussed, sleep-deprived people had some difficulty with recall, true enough, but not with the negative images. Those they could remember.
This finding is a slam-dunk link to depression. Almost by definition, depressed people are those who can remember only the negative aspects of their lives. The link goes further. For instance, people who suffer from sleep apnea, a common breathing malfunction that causes them to lose sleep, often also suffer from depression. But Stickgold says that one study, in which the apnea was successfully medicated and the depression was not, revealed that the depression corrected itself—showing that ensuring a good night’s sleep cured the depression.
This phenomenon is especially pronounced in a particular area of emotional memory processing in those who suffer from post-traumatic stress disorder, a problem much larger than a Snickers bar habit for Iraq War veterans. One line of research demonstrated that people who were truck drivers during the war did not suffer nearly the levels of PTSD that other veterans did. This was because the military had a rule that truck drivers had to sleep eight hours in every twenty-four, and the rule was enforced.
We know now that PTSD is a creature of memory, a disease of memory. Sufferers are unable to process and assign their traumatic events to the past and so are condemned to relive these terrifying scenes day after day as real and present threats. Sleep’s power over memory, however, can allow soldiers who have been through frightening and wrenching experiences to relegate them to their proper place in memory, where the events become just bad memories, not present threats.
So what do we do about all of this? Stickgold has a prescription and is, in fact, rather blunt about it: everyone needs eight and a half hours of sleep out of every twenty-four. Everybody. Further, it is more or less impossible to oversleep. That is, if you need an alarm clock to wake up every day, if you can’t get rolling until after the third or fourth shot of espresso, and you find that you sleep long and hard on weekends, then you are probably not getting enough sleep. I
n this regard, the body is wonderfully homeostatic; that is, it has strong measures and mechanisms to enforce its need for sleep. It’s almost as simple as this: if you are sleepy, sleep.
BEVERLY TATUM’S STORY
We met Beverly Daniel Tatum at Rancho La Puerta, a wellness retreat near San Diego that centers its methods on getting people back in touch with their better nature by putting them in contact with nature. But the path that brought her there began with a good night’s sleep, and ultimately that path leads to the well-being of thousands of young women, because she is president of Spelman College. Tatum was taking one of her regular fitness breaks at Rancho La Puerta, part of her program to take care of herself so she can better do her job and take care of others, which she learned to do through direct experience.
Before she came to Spelman, Tatum was a dean at Mount Holyoke College, and that job placed some heavy demands on her time that she met by spending, as many of us do, too many late-night hours in front of a computer answering email. The emails multiplied when she became president of Spelman, a four-year college historically for African American women that’s located in Atlanta, Georgia. So did the requisite official breakfasts, lunches, and dinners, which she calls “state dinners.” So she was getting four or five hours of sleep a night, cutting back on her exercise, and she put on what she calls the “presidential twenty,” not just the freshman fifteen familiar to many college students.
Tatum took a vacation in 2005 and realized that her weight gain was somehow tied to the long hours, just as Stickgold says—and she decided that she needed to take control. She set for herself a hard, fast rule to shut off her computer at 10 p.m. and go to bed. She slept at least seven to eight hours per night, regained her exercise habits, and soon began to lose some weight. She had more energy, felt better still, and saw that a lot of her students had the same problem she had had.
“I told them we’re investing a lot in your education here,” she said. “We want you to live long enough to get a return on our investment.” Her dire warning was not conjecture. She had already learned that the obesity problem left her student body with high rates of diabetes and heart disease, to the point where she was going to the funerals of alumnae in their thirties.
So Tatum went ahead with a controversial decision to end Spelman’s participation in the NCAA and organized collegiate sports, a move that made national news. Instead, she launched a comprehensive program of fitness and nutrition awareness campus-wide, designed to get students moving and eating well. And so twenty-one hundred students, future leaders, get the message and a better life, and this is how it builds. This is how change happens.
That path for change for Tatum began with a single step, which she calls a “lever.” She pulled a single lever, and in her case, it happened to be sleep—but that gave her the foundation to embrace better nutrition and exercise. It all hangs together. And ultimately, her improved well-being manifested itself as service to the well-being of others. This is our model, and its context is nature, the wild.
THE SOCIAL CONTEXT
So sleep is good, but sleep how? In what environment? It turns out that the question of how is as relevant as how much. Much of the research has illuminated the complexity of sleep. We sleep in discrete stages, each marked by clear and distinctive patterns of brain activity. Further, some of these stages correlate with specific benefits. This means that a particular stage is necessary for learning or for memory consolidation, for instance, and if you disrupt sleep in ways that deprive a person of that specific stage, the benefits linked to that stage do not accrue, even if the total sleep is at the golden average of eight and a half hours per night. This shows that there is a quality issue at work here, and this is where we are left in the dark. We really don’t know what normal sleep is, but we have some strong signals that the way we do it, a single, solitary, silent stretch, eleven until seven thirty, entombed in retreat from all others, is downright freakish behavior in terms of the human condition and human evolution. Might this habit of ours cause troubles? Maybe our dreams can tell us something about this.
At least when considered in one aspect, sleep is not a peaceful proposition. We dream about bad things. And the research on this matter is interesting: acts of aggression and threats and violence are overrepresented on our list of dream topics. We are more likely to dream about a thug threatening us with violence than a sunny day in a meadow with bunnies and butterflies. For instance, one study found that acts of aggression constituted about 45 percent of the dream content of one sample of people—by far the dominant dream category. In those cases, the dreamer was directly involved in the aggression about 80 percent of the time and was more often than not the victim. However, this burden of fright is not equally shared among all humans, although there are some common elements between genders and among adults. With both genders, the attacker in a violent dream tends to be a male or group of males or an animal, with animals in the minority, at least among modern adults.
This analysis gets far more interesting in the case of children, for whom the scary element tends to be overrepresented as animals. Further, the animal content of younger people’s dreams tends to be skewed to the violent and threatening. Dogs, horses, and cats are underrepresented, while snakes, spiders, gorillas, lions, tigers, and bears make far more frequent appearances. More telling still, there is an age gradation to both of these factors. That is, dreams of situations involving threats from animals are more common among the very youngest children and taper gradually as children move toward adulthood. In effect, children—and this is true across cultures—slowly adjust their dream content to the realities of their world. It seems as if they are born afraid of attacks from aggressive animals and gradually substitute bad guys with sticks and guns for lions. But still, threatening situations are overrepresented.
That this is true, even of children who have never seen a wild animal and have no reason to fear an attack, suggests something quite innate, a hardwired memory of conditions more realistic in evolutionary time, when children and adults both had every reason to fear animal attacks. This can seem a bit preposterous to the modern, rational mind, but probably only because we are talking about dreams. There is plenty of nonsense, superstition, and speculation involved in the topic of dreams through the years, and so there’s every reason to be suspicious. Nonetheless, there is a parallel and well-established phenomenon among the waking, and not just among humans but among other primates as well. Take a city-bred, born-and-raised denizen of concrete for his first walk through the desert, and then surreptitiously toss a live snake in his path. The reaction will be quick and predictable, regardless of whether your subject has ever seen a snake before. Same is true of chimps raised in cages. We have instincts, animal instincts, and this is demonstrable.
Yet even more interesting is the maintenance and sharpening of these very instincts among people living where the instincts come in handy, and this is borne out in the dreaming research as well. The closest we can possibly come to knowing about how our ancestors dreamed is through studies of contemporary hunters and gatherers, and it turns out that this has been done at least twice: once with aboriginals in Australia and once with the Mehinaku Indians of central Brazil, before there had been significant contact with the outside world. The latter case proved especially informative because these people actually valued dreams, so they were careful to note content and often talked about dreams with one another. In both Brazil and Australia, animals and aggression were overrepresented in dream content. In both countries, people dreamed about animals far more often than similar samples of civilized humans did, but at about the same rate as civilized children did, indicating that the decline of animals in dreams as we age is indeed an adjustment to our civilized, tamed world. We enter the world programmed to dream of the wild, but civilization takes those dreams away.
But just as important, the gender differences are alike among both hunter-gatherers and the civilized. In both cases, aggression and animals loom larger in the dr
eams of men.
Antti Revonsuo, who compiled and analyzed this large body of research in an important paper, concludes that this is really about something other than fear and trauma. Rather, it is far more in line with the main body of research on sleep in general. In his view, sleep is not a retreat to helplessness, but rather a functioning part of our learning process when the brain works through problems and devises solutions. Humans evolved among predators. Our formative years were not spent at the top of the food chain, a factor we think is too often glossed over in formulating the just-so stories about human evolution. Modern humans have forgotten what it is like to be meat, and being prey must have entailed terrors beyond imagination, particularly for the young and helpless and for the people who cared about them most.
We can begin to imagine this state of being through extrapolation, especially those of us who have seen lions or grizzly bears or Siberian tigers in the wild (all, in fact, still posing a significant threat to some humans). And yet these animals were far more numerous during humanity’s history than they are now, and they were joined or preceded by even more formidable predators, now extinct. For instance, modern-day !Kung people fall prey more often to leopards than to lions, but ancestor leopards of that place were in fact much larger, giant leopards, with every bit the speed and prowess of the more compact variety that still kills people. Even North American native people encountered saber-toothed tigers and short-faced bears, which were larger and faster than modern grizzly bears.
In such an environment, skills for dealing with predators would have been highly adaptive, to say the least, and that is exactly what determined the content of our dreams. Revonsuo believes that dreams served as a rehearsal of challenging events, to allow our brains to work at night on the reactions and skills necessary to deal with our most important threats. He concludes:
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