Sleep

ASLEEP AT THE WHEEL

Matt, in his own words

When Matt Utesch reminisces about childhood, he remembers having a lot of energy. “I was the kid that would wake up at 6:00 a.m. and watch cartoons,” Matt recalls. As a teenager, Matt channeled his energy through sports—playing basketball, running cross-country, and competing in one of the nation’s top-ranking private soccer leagues. But everything changed during Matt’s sophomore year of high school. That was the year the sleepiness hit.

Sleep Troubles Matt Utesch was active and full of energy as a child, but come sophomore year in high school, he periodically fell asleep throughout the day. Matt was beginning to experience the symptoms of a serious sleep disorder.

Courtesy Matthew Utesch

At first it seemed like nothing serious. Matt just dozed off in class from time to time. But his mini-naps gradually became more frequent. Eventually, the sleepiness would take hold of him in every class except physical education. “Matt, you just fell asleep,” his friends would say. “No I didn’t,” he would shoot back, unaware he had been sleeping. Most of Matt’s teachers assumed he was just another teenager exhausted from late-night partying. Some even slammed their hands on his desk to rouse him. Nobody, not even Matt’s doctor, suspected he had a serious medical condition—until the accident happened.

It was the summer before junior year, and Matt was driving his truck home from work at his father’s appliance repair shop. One moment he was rolling along the street at a safe distance from other cars, and the next he was ramming into a brown Saturn that had slowed to make a left turn. What had transpired in the interim? Matt had fallen asleep. He slammed on the brake pedal, but it was too late; the two vehicles collided. Unharmed, Matt leaped out of his truck and ran to check on the other driver—a woman who, as he remembers, “was totally out of it.” Her backrest had broken, and her back had nearly broken along with it. This woman already had a serious back problem, and a fresh injury was the last thing she needed. Matt was dismayed. A few weeks after the accident, he went to the woman’s home to bring her flowers. She invited him inside, and they sat down and began to chat. Then, right in the midst of their conversation, Matt fell asleep. More on Matt’s story in a bit.

An Introduction to Sleep

Animal Sleep Two mustang fillies sleep while standing. Horses are not the only animals that snooze in seemingly awkward positions. The bottlenose dolphin dozes while swimming, one brain hemisphere awake and the other asleep (McCormick, 2007; Siegel, 2005).

J. L. Klein & M. L. Hubert/Science Source

All animals sleep or engage in some rest activity that resembles sleep (Horne, 2006). Dolphins snooze while swimming, keeping one eye cracked open at all times; horses usually sleep standing up; and some birds appear to doze mid-flight (U.S. Fish & Wildlife Service, 2006). There are animals that require loads of sleep—bats and opossums sleep 18 to 20 hours a day—and those that need barely any—elephants and giraffes get by on 3 or 4 hours (Siegel, 2005). Sleep needs vary greatly among people, ranging from as little as 4 hours a night to as long as 11 or more (Horne, 2006). But most of us require between 7 and 8 hours to stay mentally and physically healthy (Banks & Dinges, 2007). Do the math and that translates to more or less a third of the day. And that translates to a third of your life. Clearly, sleep must serve some important function, but what is it? And how does it relate to consciousness? How can sleep go so wrong, as happened for Matt? We will address these questions and many more in the pages to come, but first let’s cover the basics.

Have you ever noticed that you often get sleepy in the middle of the afternoon? Even if you had a good sleep the night before, an afternoon daze invariably sets in at 2:00 or 3:00 p.m.; it’s like clockwork. That’s because it is clockwork. Many things your body does, including sleep, are regulated by a biological clock. Body temperature rises during the day, reaching its maximum in the early evening. Hormones are secreted in a cyclical fashion. Growth hormone is released at night, and levels of the stress hormone cortisol soar in the morning, reaching levels 10 to 20 times higher than at night (Wright, 2002). These are just a few of the body functions that follow predictable daily patterns affecting our behaviors, alertness, and activity levels. Such patterns in our physiological functioning roughly follow the 24-hour cycle of daylight and darkness, driven by our circadian rhythm (sər-′kā-dē-ən).

In the circadian rhythm for sleep and wakefulness, there are two times when the desire for sleep hits hardest. The first is between 2:00 and 6:00 a.m., the same window of time when most car accidents caused by sleepiness occur (Horne, 2006). The second, less intense desire for sleep strikes mid-afternoon, around 2:30 p.m., when many college students have trouble keeping their eyes open in class (Mitler & Miller, 1996).

Not all biological rhythms are circadian. Some occur over longer time intervals (monthly menstruation), and others cycle much faster (the 90-minute sleep cycles, to be discussed shortly). Many animals migrate or hibernate during certain seasons and mate according to a yearly pattern. Even when deprived of cues like changing levels of sunlight, some animals continue to follow these cycles. Birds caged indoors, for example, exhibit mood and behavioral changes at the times of year when they would normally be migrating (Wright, 2002). Biological clocks are everywhere in nature, acting as day planners for organisms as basic as bacteria and slime mold.

Where in the body do these inner clocks and calendars dwell? Miniclocks are found in cells all over your body, but a master clock is nestled deep within the hypothalamus, a brain structure whose activities revolve around maintaining homeostasis, or balance, in the body’s systems. This king of clocks, known as the suprachiasmatic nucleus (SCN), actually consists of two clusters, each no bigger than an ant, totaling around 20,000 neurons (Forger & Peskin, 2003; Wright, 2002). The SCN plays a role in our circadian rhythm by communicating with other areas of the hypothalamus, which regulates daily patterns of hunger and temperature, and the reticular formation, which regulates alertness and sleepiness (Infographic 4.1).

Although tucked away in the recesses of the brain, the SCN knows the difference between day and night. That’s because it receives signals from a special type of light-sensing cells in the eye, called retinal ganglion cells. With the help of these informants, the clock resets to the light and dark cycling of the planet. When light beams upon the earth, your clock tells you to rise and shine, and when darkness hits, it urges you to bed. One way the SCN keeps you on schedule is by indirectly communicating with the pineal gland, a part of the endocrine system, to regulate the release of melatonin, a hormone that promotes sleep. In dark conditions, the clock commands the pineal gland to produce melatonin, making it easier to sleep. When light hits the eye, melatonin secretion slows down. So if you want to sleep, turn down the lights, and let your brain turn up the melatonin.

What would happen if you lived in a dark cave with no watches or computers to help you keep track of time? Would your body stay on a 24-hour cycle or get confused? Studies of people living in conditions with no indication of the time of day show that the internal clock continues to hum along at a slightly slower pace, eventually settling on a cycle that runs a little over 24 hours (Carskadon, Labayak, Acebo, & Seifer, 1999; Czeisler et al., 1999). But depriving the clock of its external light cues is generally not a good idea. Sleep–wake cycles can be disrupted, leading to exhaustion, irritability, impairment of memory, and other negative outcomes.

INFOGRAPHIC 4.1: The Suprachiasmatic Nucleus

The suprachiasmatic nucleus (SCN) of the hypothalamus is the body’s internal master clock, playing a role in regulating our circadian rhythms. These rhythms roughly follow the 24-hour cycle of daylight and darkness. But one doesn’t have to consciously perceive light for the SCN to function properly; there is a dedicated, nonvisual pathway that carries light information from the eyes to the SCN.

Credits: Head, ©Alamy; Control room, ©Hank Morgan/Science Source

Jet Lag Rapidly traveling through time zones puts a strain on the body and brain. It takes time for us to adjust to a new time zone—typically 1 or 2 hours per day (Cunha & Stöppler, 2011).

©Beard & Howell/Getty Images

Everyone has his own unique clock, which helps explain why some of us are “morning people” or so-called larks, and others are “night owls.” If you are a lark, likely you roll out of bed feeling energized and alert, get more accomplished early in the day, yet grow weary as the day drags on. One study characterized larks as preferring to go to bed before 11:00 p.m. and rising before 8:00 a.m. (Gale & Martyn, 1998). Owls, on the other hand, get up late and hit the sack late. If you slam the “snooze” button on your alarm clock five times every morning, shower with your eyes closed, and act like a grouch at breakfast, you’re probably an owl. But being an owl often means your energy level builds throughout the day, making it easy to stay up late watching movies or reading your textbook. About 20% of us are true owls, 20% are genuine larks, and the rest fall somewhere in between (Horne, 2006).

Whether you are a lark or an owl, your clock is likely to become confused when you travel between time zones. If you take an airplane halfway around the globe, your biological clock does not automatically reset to match the new time. The physical and mental consequences of this delayed adjustment are known as “jet lag,” and it is not an ideal way to start a business trip or honeymoon, as typical symptoms include difficulty concentrating, headaches, and gastrointestinal distress. Fortunately, the biological clock can readjust by about 1 or 2 hours each day, eventually falling into step with the new environmental schedule (Cunha & Stöppler, 2011). Jet lag is frustrating, but at least it’s only temporary.

Night Shift Factory workers are among the many professionals who clock in and out at all hours of the day. Working alternating or night shifts can disrupt circadian rhythms, leading to fatigue, irritability, and diminished mental sharpness. Physical activity and good sleep habits will help counteract the negative effects (Costa, 2003).

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Now imagine plodding through life with a case of jet lag you just can’t shake. This is the tough reality for some of the world’s shift workers—firefighters, nurses, miners, power plant operators, and other professionals who work while the rest of the world is snuggled under the covers. Shift workers represent about 20% of the workforce in the United States and other developed countries, or 1 in 5 people who are employed (Di Lorenzo et al., 2003). Some work rotating shifts, which means they are constantly going to bed and waking up at different times; others consistently work the overnight shift, so their sleep–wake cycles are permanently out-of-step with the light and dark cycles of the earth. Constantly fighting the clock takes a heavy toll on the mind and body. An irregular sleep schedule may lead to symptoms of insomnia, or difficulty falling asleep and sleeping soundly. It’s not hard to imagine why. Picture yourself coming off the nightshift and arriving home at 7:00 a.m.: The sun is shining brightly, the birds are chirping, and the rest of the family is chatting over their cornflakes. This is not an ideal environment for sleep. Insomnia resulting from shift work can lead to decreased job productivity, depression, anxiety, diabetes, and other chronic diseases (Morin et al., 2006; Vgontzas et al., 2009). Studies also show that shift workers face an elevated risk of becoming overweight, and developing stomach ulcers and heart disease (Di Lorenzo et al., 2003; Knutsson, 2003). In addition, an estimated 5% to 10% of shift workers have been diagnosed with circadian rhythm sleep–wake disorders, which are characterized by excessive sleepiness at work and insomnia at home (American Psychiatric Association [APA], 2013).

Sleep Waves A young man snoozes in a sleep laboratory. The electrodes attached to his head pick up electrical activity from his brain, which is transformed into a series of spikes on a computer screen. Through careful study of these brain waves, researchers have come to understand the various stages of sleep.

Hank Morgan/Science Source

However, in our world of 24-hour pharmacies and round-the-clock customer service, shift work is a necessary evil. Dr. Lawrence J. Epstein, the director of the Sleep HealthCenters associated with Harvard, suggests ways in which night workers can minimize circadian disturbances and increase their productivity. Remember that light is the master clock’s most important external cue. Dr. Epstein suggests maximizing light exposure during work time and steering clear of it close to bedtime. Some night shifters don sunglasses on their way home, to block the morning sun, and head straight to bed in a quiet, dark room (Epstein & Mardon, 2007). Taking 20- to 30-minute power naps in the middle of a night shift can also help shift workers stay awake and alert (Harvard Medical School, 2007).

The Stages of Sleep

Have you ever watched someone sleeping? The person looks blissfully tranquil: body still, face relaxed, chest rising and falling like a lazy ocean wave. Don’t be fooled. Underneath the body’s quiet front is a very active brain, as determined by an electroencephalogram (EEG), a device that picks up electrical signals from the brain and displays this information on a screen. If you could look at an EEG trace of your brain right this moment, you would probably see a series of tiny, short spikes in rapid-fire succession. These high-frequency brainwaves are called beta waves, and they appear when you are solving a math problem, reading a book, or whenever you are alert. Now let’s say you climb into bed, close your eyes, and relax. As you become more and more drowsy, the electrical activity measured by an EEG would likely begin showing alpha waves, which are lower in frequency than beta waves (Cantero, Atienza, Salas, & Gomez, 1999). At some point, you drift into a different level of consciousness known as sleep.

A normal sleeper begins the night in non-rapid eye movement (non-REM), or nondreaming, sleep, which has four stages (Infographic 4.2). The first and lightest is Stage 1 sleep, also known as “light sleep.” During Stage 1, muscles go limp and body temperature starts to fall. The eyeballs may move gently beneath the lids. If you looked at an EEG of a person in Stage 1, you would likely see theta waves, which are lower in frequency than both alpha and beta waves. This is the type of sleep many people deny having. Example: Your friend begins to snore while watching TV, so you poke her in the ribs and say, “Wake up!” but she swears she wasn’t asleep. It is also during this initial phase of sleep that hallucinations, or imaginary sensations, can occur. Do you ever see blotches of color or bizarre images floating past while you drift off to sleep? Or perhaps you have felt a sensation of falling or swinging and then jerked your arms or legs in response? False perceptions that occur during the limbo between wakefulness and sleep are called hypnagogic hallucinations, and they are no cause for concern, in most cases. More on this when we return to Matt’s story.

After a few minutes in Stage 1, you move on to the next phase of non-REM sleep, called Stage 2 sleep, which is slightly deeper than Stage 1, so it is harder to awaken the sleeper. Theta waves continue showing up on the EEG, along with little bursts of electrical activity called sleep spindles and large waves called K-complexes appearing every 2 minutes or so. Researchers suspect sleep spindles are associated with memory consolidation and intelligence (Fogel & Smith, 2011). The exact function of K-complexes is up for debate: Some suggest they are the brain’s way of being ready to awaken when the need arises, others believe they are the mechanism for remaining asleep in spite of disturbing stimuli (Colrain, 2005).

After passing through Stages 1 and 2, the sleeper descends into Stage 3, and then into an even deeper Stage 4, when it is most difficult to awaken. Both Stages 3 and 4 are known as slow-wave sleep, because they are characterized by tall, low-frequency delta waves. Stages 3 and 4 are really very similar, but Stage 4 contains a higher proportion of delta waves (delta waves are evident more than 50% of the time). Waking a person from slow-wave sleep is not easy, and if you succeed, be prepared. Most of us will feel groggy, disoriented, and downright irritated when jarred from a slow-wave slumber. This is also the time of greatest secretion of growth hormone, which helps children to grow taller and stronger, and to build tissue (Awikunprasert & Sittiprapaporn, 2012).

You will only remain in Stage 4 for around 40 minutes. You don’t stay in deep sleep for the remainder of the night; your sleep becomes less deep as you work your way from Stage 4 back to Stage 1. And instead of waking up, you enter the fifth stage, known as rapid eye movement (REM) sleep, so called because during this stage, a person’s eyes often dart around, even though they are closed. How else can you tell someone is in REM sleep? Brain activity changes from those slower brain waves to faster and shorter brain waves; an EEG recording of someone in REM sleep shows brain activity similar to that of a person who is wide awake. Meanwhile, the eyes make quick, sharp movements beneath the eyelids, pulse and breathing rate fluctuate, and blood flow to the genitals increases, which explains why people frequently wake up in a state of sexual arousal. Another name for REM sleep is paradoxical sleep, because the sleeper appears to be quiet and resting, but the brain is full of electrical activity. People roused from REM sleep often report having vivid, illogical dreams. Thankfully, the brain has a way of preventing us from acting out our dreams. During REM sleep, certain neurons in the brainstem control the voluntary muscles, keeping most of the body still.

Kitty Dreams This cat may be dreaming of chasing mice and birds, but its body is essentially paralyzed during REM sleep. Disable the neurons responsible for this paralysis and you will see some very interesting behavior—the cat will act out its dream.

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What would happen if the neurons responsible for disabling the muscles during REM sleep were destroyed or damaged? Researchers led by Michel Jouvet in France and Adrian Morrison in the United States found the answer to that question in the 1960s and 1970s. Both teams showed that severing these neurons in the brains of cats caused them to act out their kitty dreams. Not only did the sleeping felines stand up; they arched their backs in fury, groomed and licked themselves, and hunted imaginary mice (Jouvet, 1979; Sastre & Jouvet, 1979).

INFOGRAPHIC 4.2: Sleep

Looking in on a sleep study, you’ll see that the brain is actually very active during sleep, cycling through non-REM (NREM) stages and ending in REM sleep approximately five times during the night. Transitions between stages are clearly visible as shifts in EEG patterns.

Credits: Photo of woman wearing EEG, AJ Photo/Hop Americain/Science Photo Library; EEG waves on iPad, Science Source; IPAD Photo, Thinkstock

Graphs illustrating the human sleep cycle typically present an 8-hour time span, as shown here. But this doesn’t tell the whole story of sleep. The amount of time spent sleeping and the content of our sleep changes across the life span. And while a normal night’s sleep lasts approximately 7 hours for a healthy young adult, 30% of working adults get 6 hours or fewer of sleep per night (Centers for Disease Control and Prevention, 2012f).

Congratulations. You have just completed one sleep cycle, working your way up and down Stages 1, 2, 3, and 4 of non-REM sleep and ending with a dream-packed episode of REM. Each of these cycles lasts about 90 minutes, and the average adult sleeper loops through five of them per night. These cycles are not identical because they change in composition throughout the night. During the first two cycles, a considerable amount of time is devoted to the deep Stages 3 and 4. Halfway through the night, however, Stages 3 and 4 vanish. Meanwhile, the REM periods become progressively longer, and an adult will average approximately four to five REM cycles. The first REM episode may last a mere 5 to 10 minutes, whereas the final one may drag on for nearly a half-hour (Siegel, 2005). When all is said and done, the sleep stage where we spend the most time—nearly half the night—is Stage 2 (Epstein & Mardon, 2007). Therefore, we pack in most of our restorative sleep early in the night and most dreaming toward the end.

As we age, the makeup of our sleep cycles, or sleep architecture, changes. Older people spend less time in REM sleep and the deeply refreshing stages of non-REM sleep (3 and 4). Instead, their periods of light sleep (Stages 1 and 2, which can be interrupted easily by noises and movements) are longer (Ohayon, Carskadon, Guilleminault, & Vitiello, 2004). This may be why many older people complain of sleeping poorly, waking up often, and feeling drowsy during the day. Not all elderly people have trouble sleeping, of course. Like most everything in life, sleep patterns vary considerably from one individual to the next.

Wake Up! Some of us feel refreshed after sleeping 6 or 7 hours. Others can barely grasp a glass of orange juice without a solid 8. Sleep habits appear to be a blend of biological and environmental forces—both nature and nurture.

©Ariel Skelley/Blend Images/Corbis

Tired Teen Matt’s battle with narcolepsy climaxed during his junior year of high school. In addition to falling asleep 20 to 30 times a day, he was experiencing frequent bouts of cataplexy, or sudden episodes of muscle paralysis. Cataplexy struck Matt anytime, anywhere—up to 100 times a day.

Courtesy Matthew Utesch

Sleep Attack Eight-year-old Lucas Carlton of Liverpool, England, suffers from narcolepsy, a neurological disorder characterized by frequent bouts of uncontrollable sleepiness and other symptoms. Lucas sleeps as many as 20 hours per day.

Mercury Press/ZUMAPRESS.com

And that wasn’t all. Matt developed another debilitating symptom of narcolepsy: cataplexy, or sudden episodes of total loss of muscle tone or strength that occur when a person is awake. During a severe cataplectic attack, some muscles go limp, and the body may collapse slowly to the floor like a rag doll. One moment Matt would be standing in the hallway laughing with friends; the next he was splayed on the floor unable to move a muscle. “It was like a tree being cut down [and] tipping over,” he recalls. Usually, cataplexy wears off after several seconds, but severe attacks can render a person immobilized for minutes at a time.

Cataplexy may completely disable the body, but it produces no loss in consciousness. Even during the worst attack, Matt remained completely aware of himself and his surroundings. He could hear people talking about him; sometimes they snickered in amusement. “Kids can be cruel,” Matt says. Cataplexy attacks come on suddenly, usually during periods of emotional excitement (APA, 2013). By junior year, Matt’s cataplexy had spun out of control. He was having 60 to 100 attacks a day.

Matt also developed two other common narcolepsy symptoms: sleep paralysis and hypnagogic hallucinations. Sleep paralysis is a temporary paralysis that strikes just before falling asleep or upon waking up (APA, 2013). Recall that the body becomes paralyzed during REM sleep, but sometimes this paralysis sets in prematurely or fails to turn off on time. Picture yourself lying in bed, awake and fully aware yet unable to roll over, climb out of bed, or even wiggle a toe. You want to scream for help, but your lips won’t budge. Sleep paralysis is a common symptom of narcolepsy, but it can also strike ordinary sleepers. One study found that nearly a third of college students had experienced sleep paralysis at least once in their lives (Cheyne, Newby-Clark, & Rueffer, 1999). Episodes usually last a few seconds, but some go on for several minutes—a terrifying experience for most people.

Sleep paralysis may seem scary, but now imagine seeing bloodthirsty vampires standing at the foot of your bed just as you are about to fall asleep. Earlier we discussed the hypnagogic hallucinations people can experience during Stage 1 sleep (seeing strange images, for example). But not all hypnagogic hallucinations involve harmless blobs. They can also be realistic visions of axe murderers or space aliens trying to abduct you (McNally & Clancy, 2005). Matt had a recurring hallucination of a man with a butcher knife racing through his doorway, jumping onto his bed, and stabbing him in the chest. Upon awakening, he would often quiz his mother with questions like, “When is my birthday?” or “What is your license plate number?” He wanted to verify she was real, not just another character in his dream. Like sleep paralysis, vivid hypnagogic hallucinations can occur in people without narcolepsy, too. Shift work, insomnia, and sleeping face-up are all factors that appear to heighten one’s risk (Cheyne, 2002; McNally & Clancy, 2005).

Throughout junior year, Matt took various medications to control his narcolepsy, but his symptoms persisted. Narcolepsy was beginning to interfere with virtually every aspect of his life. At the beginning of high school, Matt had a 4.0 grade point average; now he was working twice as hard and earning lower grades. Playing sports had become a major health hazard because his cataplexy struck wherever and whenever, without notice. If he collapsed while sprinting down the soccer field or diving for a basketball, he might twist an ankle, break an arm, or worse. Narcolepsy also began to undermine Matt’s social life. Some of his classmates viewed him as a source of entertainment. “Hey, you’re like that guy out of Rat Race or Deuce Bigalow,” they would say, drawing on Hollywood’s inaccurate stereotypes. It was during those years that Matt realized who his true friends were. “The people that stuck with me [then] are still my close friends now,” he says. Matt’s loyal buddies learned to read the warning signs of cataplexy (for example, when he suddenly stands still and closes his eyes) and did everything possible to keep him safe, grabbing hold of his body and slowly lowering him to the ground. His buddies had his back—literally.

Sleep Disturbances

Approximately 1 in 2,500 people suffer from narcolepsy (Ohayon, 2011). It is believed to result from a failure of the brain to properly regulate sleep patterns. Normally the boundaries separating sleep and wakefulness are relatively clear—you are awake, in REM sleep, or in non-REM sleep. With narcolepsy, the lines separating these different realms of consciousness fade, allowing sleep to spill into periods of wakefulness. The loss of muscle tone during cataplexy, sleep paralysis, and dreamlike hypnagogic hallucinations experienced while falling asleep may be explained by occurrences of REM sleep in the midst of wakefulness (Attarian, Schenck, & Mahowald, 2000). In other words, REM sleep occurs in the wrong place, at the wrong time (see a summary of this and other sleep disturbances in TABLE 4.1).

Problems with REM regulation can also lead to other sleep disturbances, including REM sleep behavior disorder. The defining characteristics of this disorder include “repeated episodes of arousal often associated with vocalizations and/or complex motor behaviors arising from REM sleep” (APA, 2013, pg 408). People with REM sleep behavior disorder are much like the cats in Morrison’s and Jouvet’s experiments; something has gone awry with the brainstem mechanism responsible for paralyzing their bodies during REM sleep, so they are able to move around and act out their dreams (Schenck & Mahowald, 2002). This is not a good thing, since the dreams of REM sleep behavior disorder sufferers tend to be unusually violent and action-packed, involving fights with wild animals and other attackers (Fantini, Corona, Clerici, & Ferini-Strambi, 2005). The sleeping partners of individuals with REM sleep behavior disorder often get kicked, punched, and screamed at. According to some research, up to 65% of REM sleep behavior disorder sufferers have injured either themselves or their bedmates at one point or another. Scrapes, cuts, and bruises are common, and traumatic brain injuries have also been reported (APA, 2013; Aurora et al., 2010). REM sleep behavior disorder primarily affects older men (age 50 and up) and frequently foreshadows the development of serious neurodegenerative disorders—conditions such as Parkinson’s disease and dementia that are associated with the gradual decline and death of neurons (Boeve et al., 2007; Fantini et al., 2005; Schenck & Mahowald, 2002). More recently, women and younger people are being diagnosed with this disorder as well (APA, 2013). Sadly, many people struggling with REM sleep behavior disorder (about half, according to some estimates) develop a neurodegenerative disease within a decade of being diagnosed (Postuma et al., 2009).

Does Shaq Snore? Basketball icon Shaquille O’Neal suffers from a breathing-related sleep disorder. At the request of Harvard researchers who studied his sleep behaviors, Shaq began wearing a special mask to keep his airway open at night. He now reports sleeping better and feeling more energized during the day (American Academy of Sleep Medicine, 2011; National Heart, Lung, and Blood Institute, 2011).

Robyn Beck/AFP/Getty Images

There are several breathing related sleep disorders, but the most common is obstructive sleep apnea hypopnea (hī-′pop-nē-s). This is a serious disturbance characterized by a complete absence of air flow (apnea) or reduced air flow (hypopnea). During normal sleep, the airway remains open, allowing air to flow in and out of the lungs. With obstructive sleep apnea hypopnea, the upper throat muscles go limp, allowing the upper airway to close shut (APA, 2013). Breathing stops for 10 seconds or more, causing blood oxygen levels to drop (Chung & Elsaid, 2009). Sensing an emergency, the brain responds by commanding the body to wake up and breathe! The sleeper awakes and gasps for air, sometimes with a noisy nasal sound, and then drifts back to sleep. This process can repeat itself several hundred times per night, preventing a person from experiencing the deep stages of sleep so crucial for feeling rested and refreshed in the morning. Most people have no memory of the repeated awakenings and wonder why they feel so exhausted during the day, with absolutely no idea they suffer from a serious sleep disturbance. Obstructive sleep apnea hypopnea is more common among men than women and is linked to increased risk of death in the elderly, increased traffic accidents, and reduced quality of life. This disorder is also associated with a rise in blood pressure, increasing the risk of cardiovascular disease. Research indicates that obstructive sleep apnea hypopnea is more prevalent in the obese, and in women after menopause (APA, 2013).

The most prevalent sleep disorder is insomnia, which is characterized by an inability to fall asleep or stay asleep; often people with insomnia will report that the quantity or quality of their sleep is not good. Some may complain they wake up too early and can’t fall back to sleep, or they don’t feel refreshed after a night’s sleep. Sleepiness during the day and difficulties with cognitive tasks and processes are also reported (APA, 2013). About a third of adults experience some symptoms of insomnia, and 6% to 10% suffer from insomnia disorder (APA, 2013; Mai & Buysse, 2008; Roth, 2007). Insomnia symptoms can be related to factors such as the stress of a new job, college studies, depression, anxiety, jet lag, aging, and drug use.

Restless Clooney George Clooney glows as he accepts the Best Actor award at the 2012 Golden Globes. You would never guess that he struggles with two of the symptoms of insomnia: difficulty falling asleep and remaining asleep (Roth, 2007). Clooney says he needs to keep the television on to fall asleep and wakes up five times a night (The Hollywood Reporter, 2012, February 15).

©Paul Drinkwater/NBC/NBCU Photo Bank via Getty Images

Peter Steiner/The New Yorker Collection/www.cartoonbank.com

Nightmares are frightening dreams that occur in REM sleep. They affect people of all ages. And unlike night terrors, nightmares can often be recalled in vivid detail. Because nightmares usually occur during REM sleep, they are generally not acted out (APA, 2013). But can nightmares cause any type of emotional harm?

A common sleep disturbance that can occur during non-REM (typically, Stages 3 and 4) is sleepwalking. A quarter of all children will experience at least one sleepwalking incident, and it seems to run in families (Licis, Desruisseau, Yamada, Duntley, & Gurnett, 2011). Here are some ways to spot a sleepwalker: Her face is expressionless; her eyes are open; and she may sit up in bed, walk around in confusion, or speak gibberish. (The garbled speech of sleepwalking is different from sleep talking, which can occur in either REM or non-REM sleep, but is not considered a sleep disturbance.) Sleepwalkers may have “limited recall” of the event upon awakening (APA, 2013). They are capable of accomplishing a variety of tasks such as opening doors, going to the bathroom, and getting dressed, all of which they are likely to forget by morning. Most sleepwalking episodes are not related to dreaming, and contrary to urban myth, awakening a sleepwalker will not cause sudden death or injury. What’s dangerous is leaving the front door unlocked and the car keys in the ignition, as sleepwalkers have been known to wander into the streets and even attempt driving (APA, 2013).

Sleep terrors are a non-REM sleep disturbance primarily affecting children. Here’s how a sleep terror typically presents itself: A child sits bolt upright in bed, staring fearfully at nothing, and utters a blood-curdling scream. Parents rush into the room to find the child crying hysterically, hyperventilating, and perhaps struggling frantically. No matter what the parents say or do, the child remains inconsolable. Fortunately, sleep terrors only last a few minutes, and most children outgrow them. Sleep terrors are often worse for parents, who are awakened by a screaming child, than they are for the child, who generally won’t remember the episode the next day (APA, 2013).

Who Needs Sleep?

Matt’s worst struggle with narcolepsy stretched through the last two years of high school. During this time, he was averaging 20 to 30 naps a day. You might think that someone who falls asleep so often would at least benefit from feeling well-rested while awake. This was not the case. Matt had trouble sleeping at night, and it was taking a heavy toll on his ability to think clearly. He remembers nodding off at the wheel a few times but continuing to drive, reassuring himself that everything was fine. (Such a decision was a poor one given that his narcolepsy had already caused at least one serious accident.) He forgot about homework assignments and simple things people told him. Matt was experiencing two of the most common symptoms of sleep deprivation: impaired judgment and lapses in memory (Goel, Rao, Durmer, & Dinges, 2009).

Let’s face it. No one can function optimally without a good night’s sleep. But the expression “good night’s sleep” means something quite different from one person to the next. Newborns sleep anywhere from 10.5 to 18 hours per day, toddlers 12 to 14 hours, school-aged children 10 to 11 hours, and teens about 9 hours (National Sleep Foundation, 2012a, 2012b). The average adult needs between 7 and 8 hours to feel restored, though others (including Madonna and Jay Leno) claim they get by on just 4 (Breus, 2009, May 6). People who average less than 4 or more than 11 hours, otherwise known as “extreme sleepers,” are very rare (Horne, 2006).

Sleep Culture A rickshaw driver snoozes in the bright sun. Afternoon siestas are common in countries such as India and Spain, but atypical in the United States (Randall, 2012, September 22). Cultural norms regarding sleep vary significantly around the world.

©Christine Welman/Alamy

What happens to animals when they don’t sleep at all? Laboratory studies show that sleep deprivation kills rats faster than starvation (Rechtschaffen & Bergmann, 1995; Siegel, 2005). Curtailing sleep in humans leads to rapid deterioration of mental and physical well-being. Stay up all night for 48 hours and you can expect your memory, attention, reaction time, and decision making to suffer noticeably (Goel et al., 2009; Lim & Dinges, 2010). Sleepy people find it especially challenging to accomplish tasks that are monotonous and boring; sleep deprivation impairs the ability to focus attention on a single activity, such as keeping your eyes on the road while driving (Lim & Dinges, 2010). Using driving simulators and tests to measure alertness, hand–eye coordination, and other factors, researchers report that getting behind the wheel while sleepy is similar to driving drunk. Staying awake for just 17 to 19 consecutive hours (which many of us with demanding jobs, children, and social lives do regularly) produces the same effect as having a blood alcohol content (BAC) of 0.05%, the legal limit in many countries. Stay up a few hours beyond that, and your driving will begin to look like that of a person whose BAC is 0.10%—enough to get you arrested in the United States (Williamson & Feyer, 2000). Sleep loss also makes you more prone to microsleeps, or uncontrollable mini-naps lasting several seconds—enough time to miss a traffic light turning red. When you take sleep deprivation to the extreme, staying awake for several days at a time (11 days is the current world record, based on experimental data; Gillin, 2002, March 25), a host of disabling effects may result, including fragmented speech, cognitive deficits, mood swings, and hallucinations (Gulevich, Dement, & Johnson, 1966).

Record-Breaking Randy A half-century ago, 17-year-old Randy Gardner set the record for the longest documented period of self-imposed sleep deprivation. With the help and encouragement of two friends, and no caffeine or stimulants of any sort, the young man went 11 consecutive days without snoozing (Gulevich et al., 1966).

©San Diego History Center

Just because you don’t pull all-nighters does not mean you are immune to problems of sleep deprivation. A large proportion of people suffer from a more chronic form of sleep loss, resulting from insufficient sleep night-upon-night for weeks, months, or years. These people are less likely than their well-rested peers to exercise, eat healthy foods, have sex, and attend family events (National Sleep Foundation, 2009), and they face a greater risk for heart disease, diabetes, and weight gain (Sigurdson & Ayas, 2007). People who do not get enough sleep have decreased immune system responses and slower reaction times (Besedovsky, Lange, & Born, 2012; Orzeł-Gryglewska, 2010). Many researchers suspect the obesity epidemic currently plaguing Western countries is linked to chronic sleep deprivation. Skimping on sleep appears to disrupt appetite-regulating hormones, which may lead to excessive hunger and overeating (Willyard, 2008).

So far we have only covered sleep loss in general, but remember there are two types of sleep: REM and non-REM. What happens if only one of these is compromised? Studies show that depriving people of Stages 3 and 4 sleep leads to increased physical symptoms such as fatigue and more overall pain (Roehrs, Hyde, Blaisdell, Greenwald, & Roth, 2006). Preliminary research suggests depriving people of REM sleep in particular can cause emotional overreactions to threatening situations (Rosales-Lagarde et al., 2012). One other important thing to note is that following REM deprivation, people experience REM rebound, an increased amount of time spent in REM sleep when they finally have an opportunity to sleep in peace.

Although we spend one third of our lives sleeping and we know what goes on while we are asleep, there is disagreement on the function of sleep. Drawing from sleep deprivation studies and other types of experiments, researchers have constructed various theories to explain why we spend so much time sleeping (TABLE 4.2). Here are three of the major ones:

• The restorative theory of sleep suggests we sleep because it allows for growth and repair of the body and brain. This makes sense, given that growth hormone is secreted during non-REM sleep and protein production ramps up in the brain during REM. Some have suggested that sleep is a time for rest and replenishment of neurotransmitters, especially those important for attention and memory (Hobson, 1989).
• An evolutionary theory of sleep suggests that sleep serves an adaptive function; it evolved because it helped us survive. For much of human history, before people became accustomed to illuminating their homes, nighttime was very dark—and very unsafe—for humans, who have poor night vision compared to animals hunting for prey. Given that our predators were more threatening in the dark, it was adaptive for us to stay out of environments where we couldn’t see. The development of our circadian rhythms driving us to sleep thus served an important evolutionary purpose.
• Another compelling theory suggests that sleep helps with the consolidation of memories and learning. Researchers disagree which stage of sleep might facilitate such a process, but one thing seems clear: Without sleep, our ability to lay down complex memories, and thus learn difficult concepts, is hampered (Farthing, 1992). How do we know this? Studies show that areas of the brain excited during learning tasks are reawakened during non-REM sleep. When researchers monitored the neuronal activity of rats exploring a new environment, they noticed certain neurons firing. These same neurons became active again when the rats fell into non-REM sleep, suggesting that the neurons were involved in remembering the experience (Diekelmann & Born, 2010). Maquet (2000) found evidence of a similar phenomenon in humans. Using PET scans, he observed common patterns of brain activity when the participants were awake and learning and later while asleep.

The exact purpose of sleep has yet to be identified, but there is no denying its importance. After a couple of sleepless nights, we are grumpy, clumsy, and not able to think straight. Research has confirmed what we all know intuitively: Without good sleep, we don’t feel like ourselves.

Before moving on to the next section, look at TABLE 4.3 for some ideas on how to get better sleep.