The Secret Life of Sleep

The Secret Life of Sleep

Research focusing on the benefits to the body of exercise, sleep and good nutrition is expanding to the benefits of the same for the brain. It’s not rocket science; it’s neuroscience that’s generating the new data that can guide lifestyle choices that strengthen and protect the brain as we age and reduce the risk, even reverse, the ravages of memory loss and dementia.

In her fascinating book, The Secret Life of Sleep, Kat Duff presents the latest scientific research about the benefits of sleep:

“Most researchers agree that short-term memory is anchored and translated into long-term memory when we sleep. As the night progresses through successive cycles of SW and REM sleep, new learning is repeated and assimilated into ever-widening nets of increasingly remote and original associations. Dreams become longer, more complicated, and farther reaching. They play out what could have happened but did not, pose alternative scenarios to make right what went wrong, and bring more information to bear on the places we get stuck. In the morning, we are left with memories that are a little less accurate but more meaningful, accessible, and useful.”

And the distressing consequences of lack of good sleep:

“The National Sleep Foundation publishes annual sleep surveys, informing the public of some stunning facts about sleep in America: 20 percent of those surveyed report sleeping less than six hours a night. Approximately one-third have fallen asleep at the wheel during the past year, accounting for more than one hundred thousand accidents per year, and nearly one-third have nodded off at work during the past month, resulting in more than $18 billion dollars in lost productivity.”

And places many of the difficulties many of us have sleeping well some night or other in the context of the over-stressed, over-scheduled lives many of us lead now:

“Americans now work an average of one extra month per years than they did in 1980 and single mothers work an extra six weeks. Employees often work overtime and outside their job descriptions for fear of losing their jobs if they refuse. Cutbacks and downsizing have further increased workloads, making it all the more necessary to operate at the top of one’s game all day long, without any lapses. Fear of what one night of lost sleep could do to one’s appearance and performance the next day has become a common concern.”

Sleep can seem like an elusive resource for many of us, especially as we age, but there is good reason to hope that science and common sense together can guide us to the practical tools we can use to get a better night’s sleep, even in the midst of over-busy, stressful lives.

May these reflections inspire you to take seriously the importance of your own sleep and make the choices that will support good sleep practices that will support more resilience in every waking moment.


I’m presenting some of the discoveries and insights in The Secret Life of Sleep in 3 sections:

1) The importance of both slow wave (SW) sleep and rapid eye movement (REM) sleep for consolidating learning into memory and processing our emotional experiences;

2) The high cost of lack of sleep to the health of our individual, personal bodies and brains, and to the entire fabric of our society;

3) The dilemma that even though many factors in modern industrialized societies make it increasingly difficult to get a good night’s sleep, it’s still up to the individual to solve that problem (See exercises to practice below for some good suggestions about that.)

The Importance of Sleep for Consolidating Learning into Memory and Processing Emotional Experiences

In her book, The Secret Life of Sleep, Kat Duff reminds us that sleep is not merely an absence of waking consciousness; sleeping and dreaming are different states of consciousness that restore and heal the functioning of the brain in important ways.

“Deep, slow wave sleep (non-REM sleep) is a deep, nearly inaccessible slumber that is characterized by slow, high-amplitude, synchronized brain waves. It appears to be the most restorative form of sleep, regenerating tissues, building bones and muscles, and strengthening immunity, all of which are facilitated by the release of growth hormones and a reduction in cortisol levels. SW sleep also burns fat and maintains cardiovascular health, which explains why sleep deprivation contributes to the development of obesity and heart problems.

“Most researchers agree that short-term memory is anchored and translated into long-term memory when we sleep. The process, called memory consolidation, appears to involve two simultaneous procedures: weakening rarely used neural connections and strengthening the patterns of newly formed memories by replaying them. Neuroscientists liken it to erasing the chalkboard so new messages do not overlap and get confused with old ones. The large, slow waves that dominate SW sleep wash the board clean by reducing the number of active connections, while the brief bursts of faster activity, called ripples, inscribe the new learning. They work together to enable new memories to stand out clearly. It seems that we forget in order to remember, and we do this best when we are deeply asleep, all is quiet, our breathing slows, and the slate is clean.

“SW sleep seems to be the most necessary state of sleep. The calming, parasympathetic branch of the autonomic nervous system predominates in SW sleep, reducing metabolism, blood pressure, and heart and breath rates. SW sleep constitutes less than one-quarter of our time asleep, but it dominates the first few hours and replenishes itself faster than any other kind of sleep.

“Curiously, the amount of SW sleep we get decreases dramatically over the human lifespan. Children tend to get a lot of SW sleep essential to sustain growing bodies and brains. While SW sleep constitutes nearly 20 percent of our nightly slumber in young adulthood, it is only 3 percent by midlife. Up to one-quarter of fifty-year-olds have no SW sleep, and this percentage increases with age. Because growth hormones are secreted only during SW sleep, a reduction in deep sleep also lowers the levels of these hormones. The combination can account for many features of the aging process, including loss of muscle tone and physical strength, increased body fat, thinning of the skin, fatigue, diminished sexual desire, memory loss, and immune malfunction. No wonder the Irish say sleep is better than medicine. It would not be an exaggeration to say that SW sleep is critical to our nightly restoration and healthy aging.

“In REM (rapid eye movement) sleep, the busiest stage of sleep, the sympathetic nervous system is activated, the brain is activated; the brain is busy dreaming (whether we remember those dreams upon awakening or not).

“The prefrontal cortex, which enables us to maintain self-awareness and organize experience, goes off-line during REM sleep. As a result, we are immersed in the internally generated worlds of our dreams unconstrained by external reality.

“One of the most notable facts about REM sleep is that it engages the amygdala, part of the limbic system, popularly known as the emotional brain. The amygdala is responsible for our fight-or-flight reactions. Ordinarily, when we encounter a new situation, the thinking part of the brain, the cortex considers information received from the senses before directing the limbic system to generate an emotional reaction. However, there are times when we need to act more quickly than that, especially in the face of danger, and instinct takes over. The sense of alarm triggers a shortcut in the brain, prompting the amygdala to spring into action before all the information is sorted out.

“During REM sleep, emotionally charged events are replayed and revised without the oversight of logic, the inhibition of morals, or the intrusion of facts from our short-term memory banks. This allows a creative free play, enabling us to draw form the sum of our experiences to imaginatively correct mistake and explore new ways of handling situations.

“Neuroscientists have proposed that REM sleep evolved to do just that; rehearse and adapt inherited survival strategies. Noting that the vast majority of the dreams people remember involve threatening situations, negative dreams might function as rehearsal for similar real events, so that threat recognition and avoidance happens faster and more automatically in comparable real situations. If so, they are like the drills athletes person on a daily basis to perfect their skills.

“In this sense, REM sleep is also essential to brain plasticity, developing the nervous system by strengthening some connections and weakening others, continually rewriting he scripts by which we live our lives.

“While SW sleep preserves individual memories with relative accuracy, REM sleep assimilates these memories into what is already known. This requires several steps: extracting the gist of what was learned, connecting it to related memories, and filing it away in existing networks of knowledge, or schemas, for further use. The process has been likened to that of a change sorter separating coins into different slots for storage. Memories are distilled into familiar topics – like French grammar or the way a family pet behaves – bundled into readable chunks, and filed away for further use. In the process, we being to infer the big picture from disparate pieces of information.

“The process of making and integrating memories enable us to extract lessons from the past to prepare for future challenges. These lessons are more than mere records of experience. When connected with existing networks of knowledge, they become the very beliefs that define who we are and who we are going to be. Every time an association is made, something is learned, memory is altered, knowledge is refined, and pre-existing beliefs are usually, though not always, confirmed. It is the essence of brain plasticity and, apparently, one of the jobs REM sleep performs. The more we learn by day, the longer we spend in REM sleep that night.

“How our minds and brains decide what is worth remembering, what to call it, and where to put it, is not clear, but many think emotions play an important role. Some experiences are seared into our memory while others fade away, and the difference between the two appears to lie with the level of emotional significance. Events that threaten our survival, like the death of a loved one, a major rejection, or a natural disaster, are highlighted by the presence of adrenaline, and they stick with us, even if we wish they did not. Ecstatic experiences, be it the birth of a baby or a religious conversion, also marked by intense emotion, find room in our memory banks as well. But the cars you see on your way to work do not – unless one of them runs into you. The heightened emotional and physiological arousal of REM sleep appears to tag the salient memories, making them easier to retrieve later, while ignoring the rest.

“Psychiatrist Mathew Walker proposed in 2009 that REM sleep functions like “overnight therapy” to strip the charge from salient memories through repeated reiterations while retaining the essential learning. He called it the “sleep to forget [the emotion] and sleep to remember [the lesson] model of cognitive and emotional processing, adding that sleep is uniquely qualified to accomplish the task.

“REM sleep, in particular, is the only time during our days and nights when our levels or norepinephrine, a kind of adrenaline, plummet, reducing arousal. In this way, the charged schemas, or beliefs, by which we stake our lives, and of which we may not be consciously aware, are routinely worked and reworked, unraveled and rewoven whenever current events activate them.

“Our sense of self in the world is continually updated, for better or for worse. It may take one night, several nights, or even years of shuttling back and forth between REM and SW sleep to take the sting out of the most disturbing experiences, but we usually come to greater understanding an detachment.

“We need out dreaming time, day and night to soothe our ruffled feathers and restore emotional equilibrium. Life has a way of pushing our buttons; sleep may serve, in part, to reset them.

“When people do not get enough sleep, this process of emotional recalibration gets interrupted, especially because most of our REM sleep occurs later in the night, during the hours that tend to get cut short. Studies demonstrate that sleep-deprived people are more likely to respond to negative cues, ignore positive ones, and react impulsively and aggressively. They become more rigid mentally and emotionally, displaying knee-jerk reactions rather than thoughtful responses. As a friend of mine says, “Without enough sleep, we turn into two-year-olds.”

The High Cost of Lack of Sleep

“The demands and attractions of our 24/7 global economy are squeezing the hours out of our nights. We are losing the knack – and taste – for rest. Rejuvenating sleep has become as elusive as clean water, dark nights, fresh air, and all the other endangered resources of our natural world.

“In the 1950s and 1960s, television and radio went off the air at midnight; now, they never stop broadcasting. Computers, internet banking, and all-night convenience stores keep us plugged in to the news, business trends, and advertisement of the global economy all day and all night. Americans now average six and a half hours of sleep a night, according to surveys conducted by the National Sleep Foundation, a 20 percent decrease in the last one hundred years, and one and a half hours less than in 1960.

“Researchers have linked insufficient sleep to obesity, diabetes, heart disease, anxiety, depression, substance abuse, accidents and death. They have also demonstrated that inadequate sleep reduces our ability to pay attention, react in a timely manner, and make sound judgments. It lowers tolerance for frustration and heightens interpersonal sensitivity, making us more likely to fly off the handle over small slights, while triggering irritability and impulsivity, all of which increase the risk of serious accidents.

“Those who believe they do great on four or five hours usually do not. They just think so because sleep deprivation impairs judgment….Several consecutive nights without enough sleep can begin to wreak havoc, especially for those who ordinarily get enough. Studies have demonstrated that a week of sleeping four to five hours a night induces a cognitive impairment equivalent to a blood alcohol level of 1 percent – being legally drunk. (Italics added – LG) Performance suffers, immunity weakens, stress hormones increase, and our abilities to learn, assess situations, and respond flexibly are reduced. Behind the wheel, or in the office of the president, we become a danger to others.

“According to the Stanford Center for Sleep Studies, “Sleep is one of the most important predictor of how long you will live – as important as whether you smoke, exercise, or have high blood pressure or cholesterol. Unhealthy sleep remains America’s largest, deadliest, most costly, and least studied health problem.”

The Dilemma: Societal Causes, Individual Solutions

“The fast-paced life of anxiety and high tension many encounter in postindustrial cultures further erodes the fabric of sleep. Societies may undergo enormous social, economic, and political changes, totally transforming the lives of their members, but they leave it up to individuals to successfully adapt, stay calm, and keep sleeping.

“62% of American adults report experiencing a sleep problem a few nights a week; the top reason is job related stress. As reporter Margot Adler observed, “In today’s world, the well-rested lose respect.” In this era of high unemployment, bulging workloads, shifting schedules, union busting, and corporate downsizing, many feel they have no choice but to burn the candle at both ends.

“There are simple things societies can do, such as delaying school start times for adolescents, providing flexible work schedules of adults, changing the color of light that electronics emit, and building workplaces with windows and skylights to expose employees to daylight to improve both sleep had daytime alertness, but the political will is often lacking.”


[All from The Secret Life of Sleep]

All creatures display some form of sleep behavior, a regular time of quiet when they settle into familiar postures, lose awareness of the outside world, and rest for anywhere from two minutes to twenty hours. The universality of sleep suggests its origins are as old as animal life on earth, an estimated six hundred million years. It also implies that sleep is more than a creature comfort. It is a requirement for life on this planet.

* * * * *

Sleep and waking states are like separate countries with a common border. We cross over twice daily, remembering one world and forgetting the other, inadvertently tracing invisible residues from one into the other. The seemingly unknowable hours we spend in sleep constitute recurring gaps in our waking awareness, and the inescapabilty of sleep suggests that something important happens during these gaps. It is an occurrence that is so common, so habitual, so ubiquitous, we barely notice. Like the air we breathe, what happens during sleep we become aware of only when its quality is deteriorating.

* * * * *

When we prepare for sleep, we strip ourselves of the accoutrements of selfhood: our clothes, glasses, makeup, and false teeth. We bid goodbye to the people around us, lie down in stillness, and return to our original, solitary nakedness. As Heraclitus, the ancient Greek philosopher, observed: “The waking have one common world, but the sleeping turn aside each into a world of his own.” Once the lights are off, and our eyes closed, even the world, as we’ve known it, vanishes, and the familiar “I” evaporates. It is the nightly annihilation of daytime awareness, what Shakespeare called “the death of each day’s life.”…No one is looking out for us in sleep. We are existentially alone and required to give ourselves over to something we cannot know or even recall the next day. It takes an act of faith to fall asleep, and not everyone has it.

* * * * *

Benjamin Franklin once famously declared: “There will be sleeping enough in the grave.” Whenever I hear that quote, I imagine it was followed by something like: “So get to work, you slackers!” Franklin wanted Americans to be industrious and hardworking, if only to convince the British that they could build and run a country. His other legendary line of advice – “plough deep while sluggards sleep, and you shall have corn to sell and keep” – clearly reflected the work ethic of his Puritan ancestors, who settled the eastern seaboard and came to dominate American political and business life for the next two hundred years. Centuries later, we have new proverbs to convince us that sleep is a form of laziness we cannot afford if we are to succeed – “You snooze, you lose” and “The best don’t rest” – but they mean the same thing.

* * * * *

The oldest Hindu Upanishads, including the Prashna Upanishad, value sleep over waking life as closer and more akin to an ultimate reality. African traditions honor sleep as a time when one can commune with the dead and receive guidance. “In fact,” wrote Mircea Eliade, a Romanian scholar of world religions, “Sleep is ridiculed only in Europe, only certain European peoples consider it a symbol of laziness, of stupidity and intellectual sterility. In other cultures, sleep is regard as a state of perfect meditation, of autonomy and creation.


[All from The Secret Life of Sleep]

Sleep scientists have shown for some time that insomniacs think they sleep less than they do. Sleep expert Stanley Coren tells a great story to illustrate the point. He opened his eyes one morning believing that he had not slept a wink all night, ready to complain about it to his wife, when he noticed white powder and chunks of plaster on top of the bed. Looking up, he saw that parts of the ceiling had cracked and fallen during the night. Then he turned on the news and learned he had slept through a major earthquake, the one that struck the San Francisco Bay Area during the World Series in 1989.

* * * * *

In the 1990s, neuroscientist Matthew Walker and his associates bean monitoring the firing of neurons in the memory centers of the brains of four pink-eared, black and white laboratory rats. A computer translated their neuronal firings into sharp, staccato crackling sounds while the rats learned a circular maze to get chocolate-flavored sprinkles. Every time a rat ran the maze, the crackles sounded in a distinct, identifiable sequence.

Then, one day, when one of the rats had eaten enough sprinkles and fallen fast asleep, Walker made a remarkable discovery. The sequence of crackles the rat produced when learning the maze repeated – the same order, only twenty times faster – during brief bursts of electrical activity called ripples, which overlay the huge, slow waves of deep sleep. It appeared that this rat was replaying his memory of the maze in compressed time, as if practicing this newly learned skill in fast-forward, and the correlation was so exact, Walker and his associates were able to tell what part of the maze was being reviewed. It was the first clear neurological evident that mammals revisit important daytime learning during SW sleep.

Walker’s rats were also better at running their mazes after they slept. In fact, the amount of their improvement was proportional to the length of time spent reactivating the maze memory in SW sleep. People are not different than rodents on this score. We too improve our abilities to perform tasks and remember significant events and facts after an interval of sleep, which has prompted researchers to recommend that students take naps while studying.

* * * * *

Years ago, a piano teacher suggested I take time off my daily practice periodically because, as she said, “For some reason, people play better after they’ve slept a night or two.” Her observation was shared by the Roman orator Quintilian many centuries before, who noted that: “It is a curious fact, of which the reason is not obvious, that the interval of a single night will greatly increase the strength of the memory.” Now my piano teacher’s casual observation is backed by scientific research. Studies reveal that learning improves over the course of several nights without any practice. In fact, sleep provides the equivalent of twice as much practice. We are smarter when we wake up than when we went to bed.

* * * * *

Sleep researcher Rosalind Cartwright followed the dreams of twenty recently divorced men and women, half of whom met the criteria for depression, over five months. She discovered that those who recovered best remembered more dreams that were longer and more complex, often nitrating fragments of recent emotional experiences with older ones. They also made a gradual shift over time from playing more passive roles in their dreams to more active ones. Their dreams were like a rehearsal for recovery. Those who did not improve had shorter, more static dreams or no recall at all. While it may seem obvious to people who make a habit of attending to their dreams, Cartwright’s study was the first scientific investigation to demonstrate that the content of our dreams, not just their occurrence, plays an important role in our recovery from emotional trauma.


“After all of the theories have been explored, one fact remains: sleep is fragile. All manner of conditions (heat, cold, good food, bad food, solitude, company, noise, silence, love and the loss of love, and so on) can fray its fabric, and there is little we can do to reliably improve it, as chronic insomniacs reminds us. The fabric of sleep requires trust and a sense of safety to remain intact, and these qualities come by way of grace, good genes, viable relationships, and practice, more than anything else.

“Fortunately, our nervous systems continue to grow and learn, building new connections, discarding old ones, and facilitating shifts in hormonal balances. Just as we can learn how to play bridge, lift weights, or do the two-step, we can train ourselves to shift into and out of states of mind, body, and emotion, even to shut off the default mode network that keeps our minds busy. We can cultivate our abilities to calm down, let go, go within, and drift off, to counteract the tendencies to gear up, grab on, look out, and get ahead that are so encouraged in our society.

“To get at the root of our problems with sleep, sleep medicine professionals claim we need to make changes in the ways we live, sleep, and even think. Therapists teach stress management techniques, such as progressive muscle relaxation, self-hypnosis, meditation, and putting aside worries to calm the body and mind. This last technique reminds me of the way Napoleon Bonaparte prepared for bed. “Different subjects are arranged in my head as in a cupboard. When I wish to interrupt one train of thought, I shut that drawer and open another. Do I wish to sleep, I simply close all the drawers”

There’s no question, reducing stress in our external daytime lives is the single most effective change we can make to promote better sleeping. (Many protocols of therapy, coaching, mindfulness practice help us do that.)

However well or poorly we can do that, cultivating a sense of safety and trust in our internal world is the next most effective thing. The brain won’t let go of its vigilance to protect us – from predators or the IRS – unless we can cultivate a sense of safety within ourselves, within our home, within our relationships. We need to strengthen our own sense of resilience and capacities to cope. (A la Bouncing Back.)

And when the external stressors remain, and the worries and ruminations of the brain’s default network keep us awake at night, our next best choice may be to “close all the drawers.” Choosing to set everything aside until morning, knowing that it will all still be there in the morning (unless our sleep/dreams alter it, which is quite possible). Downshifting through meditation-yoga before we go to sleep can help with that. Cognitive-Behavioral Therapy for Sleep – catching and shifting negative thoughts, especially anxieties about not sleeping – can help with that.

Then there are the suggestions of sleep medicine specialists that, when practiced every night, may also help over time:

Plenty of exercise and exposure to natural light during the day

Avoid caffeine, alcohol, cigarettes, and heavy meals in the evening (harm reduction!)

Slow down, quiet down in evening

Go to bed and wake up at the same time every day, even on weekends

Get off all screens – TV, computer, phones – 30 minutes before going to bed

Create psychological safety through routines and familiarity

Create physical safety with locked doors and safe place to sleep

Use “sleep hygiene” equipment as needed:

Heavy curtains to block out street light

Plug in earplugs or the earbuds of an ipod

White noise machines

Eye mask

Aromatherapy pillows

Special mattress

Warm comforter but cool fresh air

Set intention: “I will awake rested, refreshed, and ready for the day.”

P.S. According to the National Sleep Foundation, 25% of all Americans take some form of sleep medication every night. Yet an analysis of sleeping pill studies conducted by the National Institutes of Health and published in 2007 revealed that sleep medications, including the nonbenzodiazepines (Ambien, Lunesta) reduce the time it takes to fall asleep by an average of 12.8 minute compared with placebos and increase the total sleep time by only 11.4 minutes. And, functioning did not improve the next day.


The Secret Life of Sleep by Kat Duff. New York: Atria Books, 2014.

A remarkable and inter-disciplinary compendium of scientific research, psychological insight, compelling narratives, archetypal myths and religious beliefs about sleep and dreams from around the world. The author spends as much time exploring the role of dreams as she does the role of sleep (and lack of). And offers practical suggestions for how to get sleep back on track and how to relish the profundity of our dreams.

The Sleep Revolution: Transforming Your Life One Night at a Time by Arianna Huffington. New York: Harmony Books, 2016. A fascinating exploration of the history, science and benefits of sleep, with insights into the necessity of our nightly slumber and how to improve it.

The National Sleep Foundation website offers a host of articles, videos and tips on the benefits of sleep and the consequences of poor sleep.