Why do we need it, and are we getting enough? The mysteries that surround sleep are not merely scientific and clinical but also cultural.
Check out this fascinating article in The New Yorker By Jerome Groopman
“When I trained to be a doctor, some four decades ago, everyone neglected sleep. “On call” duty for hospital interns began at 6 a.m. and lasted twenty-four hours; I often kept on working until early evening the next day, after which I would stumble back to my apartment and fall asleep in my clothes. The ethic was not to complain. You were being toughened up—“iron man” was the term we all used—to deal with the demands of doctoring, which did not respect the clock. But that wasn’t the only way in which sleep was disregarded. In medical school, the subject had been covered in only the most cursory way. In a class on the brain, an instructor mentioned a neural pathway, the reticular activating system, that was associated with wakefulness. In passing, he also told us about narcolepsy, a rare condition that could cause people to sink into slumber at any moment and that had other fascinating features, such as vivid hallucinations and abrupt loss of muscle control. That was it. Ordinary sleep, it seemed, was not a subject that medicine concerned itself with.
Today, interns still work difficult hours, but the medical world’s opinions on sleep have changed. There’s a field of sleep science dedicated to the biology of repose. Sleep medicine has become a specialty, with fellowship training programs and clinics devoted to caring for those suffering from sleep disorders. And these disorders are not rare. Some forty-seven million adults, according to the National Sleep Foundation, do not get a restorative night’s sleep. In the workplace, sleep deprivation results in injuries and decreased productivity, which is thought to cost the U.S. eighteen billion dollars each year. As many as 1.2 million car crashes—twenty per cent of the annual total—can be attributed to tired drivers, so it could be said that lack of sleep causes thousands of deaths and injuries every year.
These numbers have not escaped the notice of the business world, and there is now a thriving sleep industry. Pharmaceutical companies ply us with Ambien and Lunesta, and entrepreneurs have devised any number of outlandish gadgets to foster slumber. In January, merchants at the Consumer Electronics Show unveiled “smart pajamas,” containing a “bioceramics gel,” which purportedly cool off “the body’s infrared heat emissions” to foster longer, sounder sleep. There was also a respiration sensor that straps to one’s chest and features an app, which synchronizes breathing with tonal music to help lower anxiety. Gadgets that pipe relaxing “neuroacoustic sounds” into earbuds are marketed as triggering brain waves that erase the sense of time. “Smart pillows” are programmed to record the quality of the previous night’s rest and then offer tips on improvements through an app. And, if you have three thousand dollars to spare, there’s the Magnesphere, a pod, six feet in circumference, which envelops the body in allegedly restorative electromagnetic fields. Less expensive sleep aids include weighted blankets, which confer the sensation of being swaddled; customized goggles, which aim to set your circadian rhythm by shining light at various wavelengths; and mattresses that mold to your body.
Sleep, according to the Sunday Style section of the Times, is a new status symbol, a sign of prosperity and control in a frenetic world. And, as if to confirm that sleep science is an important, even trendy field, this year’s Nobel Prize in Medicine went to three researchers who deciphered the genes responsible for regulating our circadian rhythms. Still, although we may know more about sleep than ever before, it remains one of the most enigmatic phenomena in our daily lives. “Why do all forms of life, from plants, insects, sea creatures, amphibians and birds to mammals, need rest or sleep?” Meir Kryger asks in his new book, “The Mystery of Sleep” (Yale). Kryger, a professor at Yale Medical School, is a leader in the field of sleep medicine, and has treated more than thirty thousand patients with sleep problems during a career that spans four decades. He draws on this voluminous clinical experience in his book, which is an authoritative and accessible survey of what is known, what is believed, and what is still obscure about normal patterns of sleep and the conditions that disrupt it. As he readily admits, “No one has been able to declare with certainty why all life forms need sleep.”
In Chapter 4 of “The Pickwick Papers,” which appeared in serial format in April, 1836, Charles Dickens’s readers were introduced to “a fat and red-faced boy, in a state of somnolency,” named Joe. Joe works as an assistant to a carriage driver, and continually falls asleep in the middle of his tasks:
“Very extraordinary boy, that,” said Mr. Pickwick; “does he always sleep in this way?”
“Sleep!” said the old gentleman, “he’s always asleep. Goes on errands fast asleep, and snores as he waits at table.”
“How very odd!” said Mr. Pickwick.
“Ah! odd indeed,” returned the old gentleman; “I’m proud of that boy—wouldn’t part with him on any account—he’s a natural curiosity! Here, Joe—Joe—take these things away, and open another bottle—d’ye hear?”
The fat boy rose, opened his eyes, swallowed the huge piece of pie he had been in the act of masticating when he last fell asleep, and slowly obeyed his master’s orders.
Dickens’s hyperactive imagination produced hundreds of bizarre characters. In the nineteen-fifties, some researchers were reminded of Joe when they studied an obese amateur poker player who had fallen asleep in the middle of a game. They gave the man’s condition a name: Pickwickian syndrome. Subsequent study of what is now known as obesity hypoventilation syndrome has shown that Joe was a product not of Dickens’s imagination but of powers of observation so acute that the writer had accurately recorded a pathological condition more than a century before medical science took note of it. We now know that being very overweight can prevent people from breathing deeply enough and quickly enough to keep themselves supplied with oxygen. The resulting low oxygen levels and high carbon-dioxide levels explain not only why Joe is always falling asleep but also why he is red in the face.
Meir Kryger, who tells the story of Joe in his book, has been working since the nineteen-seventies on a related condition, sleep apnea, in which a person’s airway closes during sleep, breathing stops, and, starved for air, the person awakens. Apnea can lead to heart attack and stroke from decreased oxygen, and may accelerate cognitive decline in older people. Kryger writes that there are descriptions of sleep apnea that predate Dickens’s Joe. Dionysius, a tyrant who ruled the Cretan kingdom of Heraclea in the fourth century B.C., was massively overweight. Because he repeatedly fell asleep, Dionysius hired people to poke him with long, thin needles, probably to keep him breathing. Sleep apnea was once thought to be rare, but, now that there are sophisticated diagnostic tools to measure respiration and muscle contractions, it is known to afflict some two to three per cent of the U.S. population—five million men and two and a half million women. That makes it as prevalent as mental illness, and not all sufferers are obese.
The early apnea studies pioneered by Kryger and others showed that it damaged vital organs, and this work became a catalyst for medicine’s serious examination of sleep. Once it had been demonstrated that certain conditions associated with disrupted sleep could have dire clinical consequences, it became clear that sleep was a crucial factor in maintaining good health. The technology of the sleep laboratory provided insights into how other disorders can disrupt sleep, including Parkinson’s disease, esophageal reflux, hormonal dysfunction of the thyroid and pituitary glands, and traumatic brain injury. Where doctors had previously ascribed poor nighttime sleep to anxiety and daytime sleepiness to laziness or lack of motivation, they now began to view them as conditions worthy of diagnosis and treatment.
Kryger’s book usefully outlines the current state of knowledge of sleep science in humans. The biology of sleep and wakefulness is complex, involving not just the one neural circuit I learned about in medical school but numerous pathways in the brain and countless chemical mediators. Kryger condenses this intricate neuroscience to explain the mechanisms that start and stop sleep: “a wake gauge and a body clock.” Just as a car’s fuel gauge tells us when we need to refill the tank, a “wake gauge” tells us when our body is in need of sleep. The gauge begins to signal after we have been awake for about fourteen hours, and increases in intensity until the eighteen-hour mark, after which we find it hard not to fall asleep. The wake gauge operates in the brain by means of a chemical called adenosine, which is involved in energy transfer. The longer our brain is active, the more adenosine accumulates and the sleepier we feel. (The reason coffee keeps us up is that caffeine counteracts the effects of adenosine.)
The body clock synchronizes our need for sleep with the rhythms of the world around us. Daylight is the primary regulator. When light hits the eye’s retina, a wake-up signal is sent to a collection of cells in the suprachiasmatic nucleus of the brain, which keep time and monitor our sleep-wake cycle. At dusk, when light fades, the pineal gland (where Descartes believed the soul resided) releases melatonin and makes us drowsy. Melatonin regulates the circadian rhythm of a wide range of organisms; the molecule is found in bacteria, insects, jellyfish, and plants. The visual basis of human circadian rhythms is proved by the fact that people who are blind because of damage to the eye itself often have great difficulty synchronizing their body clocks, and suffer severe sleep problems, whereas people whose blindness is caused by lesions in the visual cortex (and whose eyes are undamaged) generally have a normal circadian system.
Once we’ve finally nodded off, a variety of things occur. By tracking eye movements and using electroencephalograms to measure brain waves, researchers have identified four main types of sleep and have established that we typically progress through them in cycles of about ninety minutes. The first two stages move toward so-called “slow-wave” sleep, a state during which our neocortex powers down and which is thought to be largely responsible for the feeling of being refreshed when we wake. As we come out of slow-wave sleep, we go through a period of rapid-eye-movement sleep, or rem, one of the most commonly studied phases. Kryger calls rem the “enigmatic state.” During this phase, almost all of our muscles are paralyzed, except the diaphragm, which allows us to continue to breathe, and certain sphincters at the top and bottom of our gastrointestinal tract. Meanwhile, the brain shoots off “electrical storms,” resulting in rapid movements of the eyes, and we start to have vivid dreams. All humans dream, usually three to five times a night. And every time a man dreams he has an erection; every time a woman dreams, the blood vessels of her vagina become engorged. These changes in our genitalia are apparently unrelated to sexual thoughts before sleep or to sexual content in the dreams themselves. Rather, erections and vaginal engorgement seem to be the result of the state of dreaming itself.
Even as we cycle through the various stages, our sleep is frequently interrupted by brief awakenings, called “arousals,” each lasting only seconds. Kryger writes that “healthy sleepers” typically experience about five awakenings an hour, although they do not remember them. Scientists speculate that these brief periods of wakefulness might have evolved so that we do not place ourselves in danger while asleep—suffocating under bedding, for example, or being vulnerable to attack by a predator.
Kryger offers a comprehensive analysis of physical conditions that can impair our sleep. Women may experience insomnia owing to the normal hormonal fluctuations of the menstrual cycle and to the changes in hormonal regulation that occur with menopause. (He is rightly cautious about whether so-called “andropause,” a decline in testosterone levels among one to two per cent of men as they age, also contributes to insomnia.) Restless-leg syndrome, which causes lower limbs to spontaneously move and often cramp, is associated with certain vitamin deficiencies but often occurs without a known reason. It is a common cause of disturbed sleep in the elderly, and treatment varies from replenishing the deficient vitamin to prescribing drugs that alter neurotransmitters in the brain.
But for most of us it is the mind, rather than the body, that disrupts restorative sleep. Kryger explores in depth psychological conditions that are associated with disordered sleep, as well as psychotropic medications whose side effects can prevent a restful night. He allows for the need to medicate at times with sleeping pills or melatonin, but prefers cognitive behavioral therapy, a technique that involves teaching patients to mentally prepare themselves for slumber by devising ways to bypass the thoughts that keep them awake.
There is useful advice for less chronic problems, like jet lag. Kryger explains the difference between flying east and flying west. If you take a morning flight from London to New York, you’ll most likely arrive in the afternoon, but your body thinks it’s night. He recommends avoiding sleep for more than a short nap. Instead, eat, watch movies, and, upon arrival, try to stay awake until it’s bedtime in the new location. When flying east, he recommends getting as much sleep as possible—asking the flight attendants not to interrupt you, and using earplugs and an eye mask. He offers other tips, such as shielding your eyes from sunlight until your body would normally awaken by wearing sunglasses for about two hours after landing: this helps reset the body’s clock.
The mysteries that surround sleep are not merely scientific and clinical but also cultural. In “Wild Nights” (Basic), Benjamin Reiss, a professor of English at Emory University, writes:
Sleep is both a universal need and a freely available resource for all societies and even species. So why is it the source of frustration for so many people today? Why do we spend so much time trying to manage it and medicate it, and training ourselves—and our children—how to do it correctly? And why do so many of us feel that, despite all our efforts to tame our sleep, it’s fundamentally beyond our control?
The fault, he believes, lies with our fixation on sleeping “in one straight shot through the night,” a schedule that conflicts with the natural sleep rhythms of many people. This fixation leads to “worry and micromanagement,” paradoxically worsening insomnia. Sleep aids end up causing more problems than they solve, making us “more intolerant of small changes to routine and environment, creating a society of fussy, stressed-out sleepers.”
But what is “natural” when it comes to sleep? Reiss looks to the historian A. Roger Ekirch, who, in 2001, documented that in early-modern Europe and North America the standard pattern for nighttime sleep was “segmented.” There were two periods, sometimes termed “dead sleep” and “morning sleep,” with intervals of an hour or more when the person was awake, sometimes called “the watching,” during which people might pray or read or have sex. In some indigenous societies in Nigeria, Central America, and Brazil, segmented sleep persisted into the twentieth century. Ekirch hypothesized that segmented sleep was our natural, evolutionary heritage, and that it had been disrupted in the West by the demands of industrialization, and by electricity, which made artificial lighting ubiquitous. Reiss cites Ekirch, who asserted that the fact that many people experience insomnia in the middle of the night, after a few hours of sleep, indicates that our ancestral rhythms have been disrupted by modernization.
However, other studies cited by Reiss challenge the idea of a universal model of sleep across millennia. Jerome Siegel, a neuroscientist at U.C.L.A., studied three contemporary hunter-gatherer societies in Tanzania, Namibia, and Bolivia. All of them lacked electricity and, he posited, occupied environments like those inhabited by early humans, so their sleep patterns most likely “represented the truly natural way to sleep.” None of the tribes experienced segmented sleep, but daytime naps were important, especially during the summer months. Reiss emphasizes that these tribes showed “none of the adverse health effects—including obesity, diabetes and mood disorders—that authorities so often link to sleep deprivation.”
It seems questionable that humans have so changed psychologically and physically over the millennia that what keeps us awake today didn’t exist in the past. Reiss, a professor of English, is doubtless familiar with the many reflections on sleeplessness found in Shakespeare, whose Henry IV, conscience-stricken after seizing the throne, laments, “O sleep, O gentle sleep, Nature’s soft nurse, how have I frightened thee, that thou no more will weigh my eyelids down, and steep my senses in forgetfulness?”
Reiss himself details insomnia remedies in the ancient world that included crisp lettuce leaves, nutmeg, dandelion, and onions. Restless nights existed, but, instead of swallowing Ambien or melatonin, people ingested soporific foods, following an Aristotelian belief that “warm vapors of digested food reach the brain.” Going back even further, undoubtedly the slumber of hunter-gatherers was sometimes disrupted by worry about access to food during dry seasons, say, or by envy of more successful tribe members.
Before industrialization, sleep patterns were based largely on seasonal daylight. But the idea that modern industrial society alone is responsible for our discordant forms of sleep is belied by the taxing rhythms of agrarian life. Harvests required long days and late nights; cows would have been milked in the very early mornings, and shepherds, as the hymn says, watched their flocks by night, to save them from predators. Speaking of hymns, Reiss also ignores the demands that religious rituals have long made on daily schedules. In Judaism, there are three services for prayer: morning, afternoon, and night. (A famous passage in the Passover Haggadah has a student barging in on five rabbis who were up all night discussing the Exodus, telling them that the time had come for the morning Shema.) In Islam, the muezzin calls the faithful to prayer five times a day, beginning at dawn. And among monks, nuns, and devoted Catholic laity the “liturgy of the hours” specifies prayers every three hours, from Lauds, at 3 a.m., through to Vigils, at midnight.
Reiss writes that his book’s “guiding spirit and lead witness” is Henry David Thoreau. Thoreau suffered from insomnia, and his retreat, in 1845, to a simple cabin at Walden Pond was, in part, driven by a desperate need for rest. Thoreau attributed his nightly struggles to the fact that railroads and other industrial changes had disturbed the natural environment around Concord. Reiss believes that we are victims of “the same environmentally devastating mind-set that Thoreau decried: an attitude of dominion over nature (including our own bodies) through technology and consumerism.” As the opposite of Thoreau, emblematic of everything he was reacting against, Reiss gives us Honoré de Balzac, who, while Thoreau was in Walden, was fuelling his writing with twenty to fifty cups of coffee a day, often on an empty stomach. Balzac believed that, with caffeine, “sparks shoot all the way to the brain,” and “forms and shapes and characters rear up; the paper is spread with ink.” Balzac typically wrote between fourteen and sixteen hours a day for two decades, producing sixteen volumes of “La Comédie Humaine” within six years. Thoreau rejected coffee as an artificial stimulant and suggested that communion with nature offered a superior high: “Who does not prefer to be intoxicated by the air he breathes?”
At the heart of “Wild Nights” is the tension between the stimulation of intense productivity and a longing for a lost Eden of relaxation. But did Eden ever really exist? The history of blaming modernity for lost sleep runs long. Where Thoreau once held railroads responsible for his insomnia, we now obsess over e-mail and social media and the glowing screens of our computers and smartphones. Societies have been looking for ways of forcing people to rest since at least the Iron Age, when the Sabbath tradition emerged in Judaism. As Kryger shows, sleep is utterly essential to life, organically speaking, but the act of living our lives to the fullest, with all the attendant toils, responsibilities, and worries, has probably always been the enemy of sleep. Even God needed a seventh day to rest from all that he created.”