Sleep Medicine: Medical School Crash Course

Sleep Medicine

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TABLE OF CONTENTS Preface........................................................................................................ 1 Chapter One: Sleep-Wake Patterns in Normal Adults and Children............. 5 Normal Sleep.................................................................................................................... 5 Circadian Rhythms .......................................................................................................... 8 Sleep Stages and Sleep Cycles ........................................................................................ 12 Types of Sleep Disorders................................................................................................ 14 Key Takeaways ............................................................................................................... 16 Quiz .................................................................................................................................17 Chapter Two: Sleep Physiology ................................................................. 21 Brain Physiology in Sleep .............................................................................................. 21 EEG Patterns in Sleep .................................................................................................... 24 Respiratory Patterns in Sleep ........................................................................................ 26 Cardiovascular Patterns ................................................................................................. 27 Key Takeaways ............................................................................................................... 29 Quiz ................................................................................................................................ 30 Chapter Three: Evaluating Human Sleep .................................................. 35 Polysomnography .......................................................................................................... 35 Multiple Sleep Latency Test ........................................................................................... 37 Maintenance of Wakefulness Test ................................................................................. 38 Scoring the Polysomnogram .......................................................................................... 38 Sleep Stage Scoring ........................................................................................................ 39 Key Takeaways ............................................................................................................... 41 Quiz ................................................................................................................................ 42

Chapter Four: Sleep Deprivation............................................................... 45 Introduction to Sleep Deprivation ................................................................................. 45 Manifestations of Sleep Deprivation ............................................................................. 47 Treatment....................................................................................................................... 48 Sequelae of Sleep Deprivation ....................................................................................... 50 Prevention of Sleep Deprivation .................................................................................... 51 Key Takeaways ............................................................................................................... 53 Quiz ................................................................................................................................ 54 Chapter Five: Insomnia ............................................................................. 58 Types of Insomnia .......................................................................................................... 58 Causes of Insomnia ........................................................................................................ 59 Pathophysiology of Insomnia ........................................................................................ 61 Manifestations ............................................................................................................... 62 Evaluation of Insomnia.................................................................................................. 63 Management of Insomnia .............................................................................................. 65 Prevention ...................................................................................................................... 67 Key Takeaways ............................................................................................................... 69 Quiz ................................................................................................................................ 70 Chapter Six: Hypersomnias ...................................................................... 74 Primary Hypersomnia ................................................................................................... 74 Differential Diagnosis .................................................................................................... 76 Diagnosis of Hypersomnia............................................................................................. 77 Treatment of Hypersomnia ........................................................................................... 77 Narcolepsy...................................................................................................................... 78

Pathophysiology of Narcolepsy...................................................................................... 79 Diagnosis of Narcolepsy.................................................................................................80 Epidemiology and Prognosis of Narcolepsy .................................................................. 81 Management of Narcolepsy ........................................................................................... 82 Key Takeaways ............................................................................................................... 84 Quiz ................................................................................................................................ 85 Chapter Seven: Sleep-Related Breathing Disorders ................................... 88 Obstructive Sleep Apnea ................................................................................................88 Pathophysiology of Obstructive Sleep Apnea ................................................................ 89 Epidemiology and Prognosis of OSA ............................................................................. 91 Evaluation and Workup of Obstructive Sleep Apnea .................................................... 91 Treatment of Obstructive Sleep Apnea.......................................................................... 93 Central Sleep Apnea ....................................................................................................... 95 Workup of Central Sleep Apnea .................................................................................... 97 Treatment of Central Sleep Apnea ................................................................................ 98 Key Takeaways ............................................................................................................... 99 Quiz .............................................................................................................................. 100 Chapter Eight: Circadian Rhythm Sleep Disorders .................................. 104 Types of Circadian Rhythm Sleep Disorders ............................................................... 104 Epidemiology and Prognosis of Circadian Rhythm Disorders ................................... 107 Diagnostic Workup for Circadian Rhythm Disorders ................................................. 107 Treatment for Circadian Rhythm Disturbances .......................................................... 108 Non-24-Hour Sleep-Wake Disorder............................................................................ 109 Key Takeaways .............................................................................................................. 112

Quiz ............................................................................................................................... 113 Chapter Nine: Parasomnias ..................................................................... 117 Introduction to Parasomnias ........................................................................................ 117 Night Terrors................................................................................................................. 118 Epidemiology and Prognosis ........................................................................................ 119 Major Features of Sleep Terrors .................................................................................. 120 Diagnosis of Sleep Terrors ........................................................................................... 120 Management of Sleep Terrors ..................................................................................... 120 Somnambulism or Sleepwalking .................................................................................. 121 Epidemiology and Prognosis of Sleepwalking............................................................. 122 Workup of Somnambulism .......................................................................................... 123 Management of Somnambulism ................................................................................. 123 Nightmare Disorder ..................................................................................................... 124 Epidemiology and Prognosis ....................................................................................... 124 Treatment of Nightmare Disorder ............................................................................... 125 Sleep Paralysis ............................................................................................................. 125 Key Takeaways ..............................................................................................................127 Quiz .............................................................................................................................. 128 Chapter Ten: Movement Disorders in Sleep ............................................. 131 Sleep Bruxism ............................................................................................................... 131 Epidemiology and Prognosis of Restless Legs Syndrome ........................................... 134 Treatment for Restless Legs Syndrome ....................................................................... 135 Periodic Limb Movement Disorder ............................................................................. 136 REM Sleep Movement Disorder .................................................................................. 136

Key Takeaways ............................................................................................................. 138 Quiz .............................................................................................................................. 138 Chapter Eleven: Sleep with Neurologic and Psychiatric Disorders .......... 142 Chronic Fatigue Syndrome and Sleep ......................................................................... 142 Alzheimer’s Disease and Sleep .................................................................................... 143 Pain and Sleep .............................................................................................................. 145 Depression and Sleep ................................................................................................... 148 Anxiety Disorders and Sleep ........................................................................................ 149 Schizophrenia and Sleep Disorders ............................................................................. 152 Key Takeaways ............................................................................................................. 154 Quiz ...............................................................................................................................155 Chapter Twelve: Sleep Pharmacology...................................................... 159 Basic Medications for Insomnia .................................................................................. 159 Benzodiazepines for Insomnia ..................................................................................... 161 Sedative-Hypnotic Drugs .............................................................................................. 161 Antidepressants for Insomnia ..................................................................................... 162 Antipsychotics for Insomnia ........................................................................................ 163 Stimulant Drugs ........................................................................................................... 164 Herbal Preparations for Sleep ..................................................................................... 165 Key Takeaways ............................................................................................................. 167 Quiz .............................................................................................................................. 168 Chapter Thirteen: Pediatric Sleep Disorders ............................................ 172 Overview of Pediatric Sleep Disorders .........................................................................172 Enuresis......................................................................................................................... 177

Benign Neonatal Sleep Myoclonus .............................................................................. 180 SIDS.............................................................................................................................. 180 Key Takeaways ............................................................................................................. 182 Quiz .............................................................................................................................. 183 Summary ................................................................................................ 186 Course Questions and Answers ............................................................... 190

PREFACE This course covers the main issues a healthcare provider must know about when it comes to sleep and sleep-related disorders. The prevalence of sleep disorders is high in clinical practices, both inpatient and outpatient, and many practitioners do not really know how to handle them. Through studying this course, you will come to understand what constitutes normal sleep and what the different sleep disorders are all about. The diagnosis, manifestations, and management of sleep disorders and sleep-related disorders are covered so you will come to feel competent about how to help individuals suffering from these types of problems.

The purpose of chapter one in the course is to understand what constitutes normal sleep, including why people need to sleep in the first place. The circadian rhythm is an important part of the sleep-wake cycle and regulates many aspects of sleep. When a person sleeps, they go through many different sleep stages, which together constitutes the sleep cycle. While the rest of the course is about sleep disorders, this chapter introduces the different sleep disorders and what they mean when it comes to getting quality sleep.

Chapter two looks more deeply into the physiology and neuroanatomy of sleep. There are specific brain areas associated with sleep and wakefulness, and there are certain neurotransmitters that are involved with falling asleep and maintaining sleep. There are different EEG patterns associated with the different sleep stages as well. Sleep has a remarkable effect on the respiratory system, the cardiovascular system, and the thermoregulatory system, which are covered as part of this chapter.

Chapter three in the course discusses the different ways of evaluating human sleep. The main thing that is used to evaluate sleep is the polysomnography evaluation, which is also called a sleep study. Several parameters are evaluated as part of polysomnography that look at different aspects of sleep. Sleep stage scoring is a way to evaluate the different aspects of the sleep cycle; this is also discussed as part of the chapter.

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Chapter four in the course introduces the topic of sleep deprivation by first defining what it is and what the different types of sleep deprivation there are. There are certain manifestations of sleep deprivation that define a person who is probably sleep deprived.

Besides catching up on lost sleep and getting sleep, there are different ways to treat sleep deprivation, which are covered in the chapter. The adverse effects or sequelae of sleep deprivation are also discussed at the end of the chapter; these can occur if sleep deprivation is prolonged and untreated.

The focus of chapter five is insomnia, which is the difficulty in attaining or maintaining sleep. Most people will have episodes of insomnia in their lifetime, but some individuals are chronic insomniacs. There are several different types of insomnia, which have unique symptoms and manifestations. There are different ways to diagnose insomnia and multiple treatment strategies that vary from behavioral to the use of sleeppromoting medications. There are also preventative measures to avoid insomnia, which are covered in this chapter.

Chapter six in the course covers hypersomnias or situations where the individual sleeps more than the normal amount of time or sleeps at inappropriate times. The two main hypersomnias discussed as part of this chapter are primary hypersomnia and narcolepsy. Both of these are considered neurological disorders that adversely affect the amount of sleep the person gets. These can have severe implications on daily functioning for the sufferer. The way in which these disorders are identified and treated are covered as part of this chapter.

The topics of chapter seven are obstructive sleep apnea and central sleep apnea. With obstructive sleep apnea, the patient has breathing efforts but these efforts are impeded, usually by a temporary occlusion of the upper airway. For patients who have central sleep apnea, there are apneic spells in breathing; however, the problem is related to a diminished respiratory drive. There are similarities and differences in the pathophysiology, presentation, workup, and treatment of these sleep-related breathing disorders.

Chapter eight in the course talks about those sleep disorders that are related to the normal 24-hour circadian rhythm in the human body that regulates bodily functions

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according to the time of day. The most common of these disorders is jet lag, although there are several other related disorders, including shift work sleep problems, delayed phase sleep disorder, advanced phase sleep disorder, and non-24 sleep disorder, which can happen in people who are blind. These disorders are related to one another in that each involves a problem in the timing of sleep and wakefulness.

Chapter nine takes on the topic of parasomnias. These represent specific disruptions in the normal sleep cycle that are associated with arousal from REM or non-REM sleep.

Much of the time, these disorders lead to undesirable behaviors such as sleepwalking or talking in one’s sleep. Others can be extremely distressful, such as can be seen in things like night terrors, sleep paralysis, and nightmare disorder. While these sleep problems can occur at any age, they often start early in life and persist until adulthood or until the problem is treated. There are psychological and medical treatments for these disorders that vary with the problem.

The focus of chapter ten in the course is movement disorders in sleep. These can include sleep bruxism, which is the grinding of one’s teeth during sleep, which is very common in adults and children. There are two related limb movement disorders in sleep, which are restless legs syndrome and periodic limb movement disorder—both of which can greatly disrupt sleep. REM sleep movement disorder is also called REM sleep behavior disorder can be classified as a movement disorder or parasomnia and involves acting out one’s dreams during REM sleep.

Chapter eleven discusses the different sleep disorders and sleeping problems that can exist with certain neurologic disorders and psychiatric disorders as well as the sleep difficulties that happen in individuals with acute and chronic pain. There is a strong relationship between these disorders and the development of sleep problems.

Interestingly, while people with these problems often have sleep deficits, the sleep deficits cycle back and contribute to the worsening of the medical and psychiatric disorders the patient has to begin with.

Chapter twelve in the course looks more deeply into the drugs used to treat sleep problems. There is a variety of drugs used to treat insomnia, such as benzodiazepines, sedative-hypnotic drugs, and herbal preparations that help in attaining and maintaining

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sleep. Certain antidepressants and antipsychotics are sedating and represent nonaddicting alternatives to improve sleep. For people who have narcolepsy or other causes of hypersomnia, stimulant drugs can be helpful in maintaining wakefulness.

The focus of chapter thirteen is pediatric sleep disorders. An overview of these types of disorders indicates that children have many of the same sleep disorders as adults but at a different frequency than is seen in adults. Nocturnal enuresis is almost always a disorder of children due to a relative immaturity of the nervous system and bladder mechanics. Infants can suffer from benign neonatal sleep myoclonus, which requires an adequate diagnosis but not necessarily any treatment. Also seen in infants is sudden infant death syndrome or SIDS, which is perhaps the most dangerous outcome of sleeping in neonates and young infants.

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CHAPTER ONE: SLEEP-WAKE PATTERNS IN NORMAL ADULTS AND CHILDREN The purpose of this chapter is to understand what constitutes normal sleep, including why people need to sleep in the first place. The circadian rhythm is an important part of the sleep-wake cycle and regulates many aspects of sleep. When a person sleeps, they go through many different sleep stages, which together constitutes the sleep cycle. While the rest of the course is about sleep disorders, this chapter introduces the different sleep disorders and what they mean when it comes to getting quality sleep.

NORMAL SLEEP Sleep happens nearly every night to everyone. Consciousness is lost and the individual goes through periods of time of deep sleep and dreaming. Generally, little is remembered about the passage of time but most are aware that time has passed upon awakening. All organisms go through patterns of rest and activity that mimic sleep in humans. There are certain features associated with sleep in human beings, including the following: •

It involves a period of time of reduced activity.

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There is a typical posture and closing of the eyes in sleep.

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There is a reduced responsiveness to external stimuli.

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It is relatively simple to reverse it (versus coma or hibernation).

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There are typical brainwaves associated with it.

There are certain physiological changes in the body associated with sleep, which will be covered in the next chapter. Some of these include a reduction in body temperature, and blood pressure. Oxygen uptake is less but brain wave activity, heart rate, and breath rates are variable, particularly during REM sleep or “rapid eye movement” sleep. These become more regular during non-REM sleep.

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The brain actually remains fairly active during sleep with a decreased firing rate when a patient enters the non-REM sleep stage. The overall brain wave pattern seen in nonREM sleep is relatively coordinated and synchronous compared to the wakeful sleep pattern and the REM sleep pattern. The REM sleep stage involves an increase in firing rate so that it can be more active than wakefulness. This is the period of time when much of dreaming occurs.

There are some differences among mammals who sleep. Whales and dolphins, for example, maintain some degree of consciousness when they sleep because they must resurface in order to breathe. Because of this, only one hemisphere of their brain “sleeps” at a time so there is enough consciousness for this activity.

Under wakeful states, the body temperature is regulated through shivering, blood flow shifting, and sweating. This means that there is minimal shifting of body temperature when awake. Sleep is induced when the set temperature of the body drops by about 1 to 2 degrees Fahrenheit. Less energy is necessary to maintain the body temperature and energy is conserved. Body temperature is maintained during sleep but it drops precipitously during REM sleep, when it is at its lowest.

Breathing is irregular while awake and is affected by many things. The breath rate decreases during non-REM sleep and is generally very regular. The breath rate increases during REM sleep and becomes less regular.

The blood pressure and heart rate will decrease in non-REM sleep but this isn’t the case in REM sleep. In REM sleep, the heart activity will be more variable and will more likely mimic the wakeful state. Blood flow changes will cause swelling of the clitoris and erections in women and men, respectively, during sleep. Some of these changes may directly relate to dream content.

Most of the physiological activities in the body will reduce during sleep. The production of urine decreases because of a reduction in the glomerular filtration rate. There are some processes that increase during sleep, however. Growth hormone release is increased with sleep and activities linked to cell repair, growth, and digestion will increase as part of the sleeping process.

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Dreaming is poorly understood when it comes to sleep. Both REM sleep and non-REM sleep involve dreaming. The thoughts involved in dreaming tend to be illogical, random, and sometimes bizarre. REM sleep involves more visual dreaming, while night terrors happen in non-REM sleep. While there are many ways to interpret dreams, the actual meaning of dreams is somewhat mysterious. No one really knows if dreams mean anything at all.

Sleep is part of the body’s natural programming activities. There is an internal biological clock and a sleep-wake homeostat that determine what happens when we sleep. Early sleep research indicated that, when nighttime comes, the brain shuts down and restarts when awakening in the morning. This theory was debunked when EEGs were invented in 1929. Figure 1 shows an electroencephalogram being performed:

Figure 1.

As you will see, there are several sleep stages, most broadly defined as REM sleep and non-REM sleep. The EEG in REM sleep shows small-amplitude, high-frequency waves and rapid eye movements. Most people awaken from REM sleep saying that they’ve dreamed. Fewer people awaken from NREM or non-REM sleep saying they’ve dreamed.

In general, the muscles are paralyzed during sleep so as to avoid acting out one’s dreams. There are three stages of non-REM sleep we will discuss in a minute.

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There are many different factors that influence sleep. These can include the presence of recent sleep or wakefulness, the patient’s age, the time of day, and other factors, like stress, environmental conditions, exercise, and certain chemicals. As an infant, sleep starts in REM sleep. Babies have a shorter sleep cycle, alternative between REM and non-REM sleep every 50 minutes, instead of every 90 minutes in adults.

The recent sleep history will impact the sleep pattern of a given night’s sleep. An irregular sleep schedule or missing a night’s sleep will affect the pattern of sleep so there is more non-REM sleep. Drugs like alcohol will suppress REM sleep but this rebounds as the night progresses. The more REM sleep a person has, the more frequently the person will awaken.

While it is common to get sleep in one big block, this isn’t the only possible sleep pattern. Many cultures, particularly in tropical areas, will have an afternoon nap among adults. Stores and buildings close so that people can get a one to two-hour nap.

Napping follows the largest meal of the day and occurs during the hottest time of the day. Naps in most cases are between thirty minutes and sixty minutes. It is a good way for people who do not sleep well to catch up during the day.

CIRCADIAN RHYTHMS It is generally common for adults to get 16 hours of wakefulness with 8 hours of sleep.

There is a small bundle of nerve cells that promote or initiate sleep. There are areas in the brainstem and hypothalamus that are involved in wakefulness. The tuberomammillary nucleus or TMN releases histamine to cause wakefulness. This is why anti-histamines promote sleep. Other neurons will make orexin or hypocretin that stimulates the arousal centers in the cerebral cortex.

The hypothalamic nucleus called VLPO or ventrolateral preoptic nucleus connects to the arousal centers, promoting sleep. There is mutual inhibition between the sleeppromoting neurons and the wake-promoting neurons that cause stable wakefulness or sleep. The VLPO and the TNM operate opposite to one another in order to have a normal sleep pattern.

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There are relatively rapid switches between sleep and wakefulness and between REM and non-REM sleep. It takes several minutes to relax enough to fall asleep and about 20 minutes or more to get into a deep sleep. Sleep onset, however, can occur abruptly, such as when falling asleep at the wheel. Waking up can also be abrupt, such as when an alarm goes off.

There are internal factors (like circadian rhythms) and external factors (like noise) that play a role in getting to sleep and waking up. Adenosine builds up with prolonged wakefulness, ultimately inducing sleep by blocking wake-promoting neurons. Caffeine inhibits adenosine to keep us awake.

The internal biological clock in the brain is the suprachiasmatic nucleus or SCN. This receives light signals from the eye in order to reset the sleep clock. It regulates many of the factors associated with sleep, promoting wakefulness that offsets the sleep drive. It also maintains sleep in the second half of the night, when the sleep drive has left.

The sleep drive is the natural drive to sleep when you haven’t gotten enough. It is a homeostatic mechanism that regulates the amount of sleep we get. Every waking hour we have strengthens the homeostatic sleep drive, which builds up until we absolutely have to go to sleep. The only way to overcome it is to actually sleep.

The reason we are able to stay awake for sixteen hours at a time is because of the circadian rhythm. It is controlled by a small number of neurons in the brain and is synchronized to the sleep/wake cycle. It opposes the sleep drive that normally increases with every hour that we’re awake. Only when the circadian pattern drops off does the sleep drive kick in so we can sleep.

The sleep drive is high during the first half of sleep and the alert signal is low. This means it is easy to maintain sleep. After four hours of uninterrupted sleep, the sleep drive is lowered and the alerting signal begins to kick in. When these things are coordinated, they interact in order to have a prolonged period of sleep and alertness.

We are tired after a midday meal because the alerting signal diminishes slightly. It is difficult to fall asleep between 8 and 9 pm at night, because the alerting signal is still too high.

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There are changes in the structure and function of the brain during development that affect sleep. The amount of sleep needed and the fragmentation experienced as we age changes. Stress and many different medical conditions can affect the amount of sleep we can get in real life. Medications and the food we eat also affect sleep. Light, of course, affects the suprachiasmatic nucleus and its regulation of sleep. In fact, light is one of the most important factors affecting sleep. Exposure to light in the late evening will affect the ability to sleep during that time.

Things like shift work and jet lag will change the circadian rhythm over the course of the day. This interferes with when we sleep and which sleep stages can be achieved during sleep. Jet lag and shift work will lead to insomnia and excessive sleepiness at the wrong times.

Pain, certain medical conditions, anxiety, and depression make it harder to fall asleep.

There will be lighter sleep and more REM sleep with less non-REM sleep. Stress will make restful sleep much harder to achieve by affecting the arousal response. Pain will limit the deepest stages of sleep. Medications that will impact sleep include alcohol, caffeine, antihistamines, beta blockers, nicotine, antidepressants, and alpha blockers.

Both nicotine and caffeine will inhibit sleep.

If sleep happens after taking in caffeine, the stimulant will impact the quality of sleep.

There will be decreased slow-wave sleep and REM sleep and increased awakenings.

Some people are relatively intolerant to caffeine and it will have less of an effect on sleep, especially when the sleep drive is great. Alcohol will cause falling asleep more quickly but the quality of sleep will be worse. High amounts of alcohol will cause insomnia. Sleep apnea will be worse with alcohol consumption.

There are many medications that have effects on sleep. Beta blockers will decrease REM sleep and slow-wave sleep, making you tired in the daytime. The same is true of alpha blockers. Antidepressants will decrease REM sleep but some SSRIs will promote insomnia in susceptible individuals.

The environment you sleep in has an impact on sleep quantity and quality. This includes the levels of noise, light, and temperature. Too much light will negatively impact sleep so small nightlights are beneficial. Noise can relax some people if the

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volume is low. There is no prescribed “good temperature” for sleep but extremes will disrupt sleep. REM sleep is more sensitive to temperature-related disruption in sleep.

Cold temperatures deprive us of REM sleep.

How much sleep is necessary? In general, it is about six to nine hours of sleep a night with seven hours of actual sleep being optimal. Everyone has differences in the amount of sleep they get with genetic influences commonly seen. Age, physical exertion, mental activity, and health also influence the amount of sleep people need. The recommendations are 8 hours for people between 18 and 21 years of age and 7 hours for those over 21 years.

Babies under a year need 15 to 20 hours of sleep a day. Age 1-2 years needs 14 hours of sleep. By 13 to 19 years of age, about 9 hours of sleep are needed. Seniors still need about seven to eight hours of sleep per night. Only about 32 percent of older adults are getting the amount of sleep they probably need to get.

Sleep deprivation will affect your reaction time and judgment. You can’t actually change the amount of sleep your body needs and eventually you will have to sleep in order to catch up on the sleep you miss when you are sleep deprived. In reality, only about a third to a half of all sleep is caught up when doing this. If you fall asleep within five minutes of lying down, you probably have sleep deprivation. Microsleeps or brief sleeps are another sign of sleep deprivation.

Mortality is greatest with long sleepers and short sleepers. People with sleep debt have more weight gain and depression, with worsened memory and a poorer immune system.

Those with insomnia get less deep sleep and poorer sleep quality. Insomnia is an increasing part of the aging process that may have something to do with the medications they take.

Signs of too much sleep include awakening before the alarm, taking longer than an hour to fall asleep, having low energy, having hypersomnia, and experiencing weight gain from a lack of activity. Signs of too little sleep include waking up from stress during the night, feeling worn-out, being moody, having weight gain, and being drowsy during the day. Forgetfulness can be a sign of too little sleep.

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SLEEP STAGES AND SLEEP CYCLES We’ve talked a little bit about the different sleep stages. There are about four separate sleep stages. There are three stages of non-REM sleep called 1, 2, and 3, along with REM or rapid eye movement sleep. These from a complete sleep cycle that lasts about 90 minutes each, with each stage lasting about five to fifteen minutes in total length.

The first few cycles have short REM sleeps but later on in the night, the REM sleep periods lengthen and the deep sleep non-REM sleep shortens.

Stage 1 is the lightest stage of Non-REM sleep. There are slow eye movements and easy arousability. Muscle tone decreases and brain waves slow. This is when hypnic jerks or muscle spasms are most experienced. The sensation of falling happens in this phase.

Stage 2 is the first defined stage of non-REM sleep. Slow eye roles stop and brain waves slow. There are brief bursts of brain activity called sleep spindles that are associated with K complexes. These together keep you from waking up. Body temperature drops and heart rate slows.

Stage 3 is the deepest stage of non-REM sleep. This is when you get more restorative sleep and you can get slow waves or delta waves. It is hard to awaken the person from this stage of sleep and is when sleep talking, sleep walking, and night terrors usually most occur.

REM sleep is rapid eye movement sleep, when most people do a great deal of dreaming.

There are rapid eye movements and more active brain wave patterns. It is easier to awaken a person while in REM sleep but it can leave a person feeling groggy when awakening in this stage of sleep.

One sleep cycle is the progression through the various non-REM sleep states through REM sleep and finally back again. This lasts about 90 minutes. You do not go through deep sleep directly to REM sleep. It goes from light to deep sleep and back to light sleep before going into REM sleep and starting again. There are no abrupt changes between the stages from deep to light or vice versa.

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Stage 2 lasts the longest time—about 40 to 60 percent of total sleep time. Restorative stage 3 lasts only five to fifteen percent of the time. It lasts longer in adolescents and children. REM sleep starts 90 minutes after sleep onset and is relatively short.

Deep sleep or stage 3 sleep involves the slow delta waves. It is least likely to be affected by external stimuli and is hard to wake up from. After sleep deprivation, this is the time of sleep most people sleep in in order to restore lost sleep. Bedwetting an occur in this phase of sleep because of how deep it is. It has the capacity to reduce the sleep drive the most of all of the stages. Human growth hormone is released during this phase and the immune system recovers.

A person will have about 3 to 5 REM sleep periods per night with the longest time being just before waking up. If awakening from REM sleep too early, the person will be sleepy and have sleep inertia for minutes to hours after waking up. Breathing is rapid, shallow, and irregular with jerking of the eyes. The limbs are paralyzed with brain waves similar to those when awake. Erections occur and temperature regulation diminishes. Figure 2 shows the different brain waves in the different times of sleep.

Dreams can happen in any stage but are most vivid in REM sleep. Brain waves in rem sleep are low amplitude with mixed frequencies. Individuals dream about 4 to 6 times each night, even if they do not remember their dreams. People usually remember their dreams when they awaken in the middle of REM sleep. Obstructive sleep apnea is worse during REM sleep because of the paralysis they have.

Interestingly, deprivation of REM sleep does not lead to insanity but a lack of REM sleep can help individuals who have clinical depression. The way in which REM sleep deprivation helps depression is not completely clear. REM sleep may be linked to both learning and memory, according to more recent theories on sleep.

Sleep will change throughout life. As newborns, there is a lot of REM sleep or “active” sleep that allows for frequent awakening for feeding. Infants between four months and a year sleep 10 to 13 hours a day with standard sleep stages. Toddlers spend about 25 percent of the time in stage 3 sleep and about the same amount of time in REM sleep.

Children aged 3 to 6 will sleep 9 to 10 hours of sleep per night. Older children spend more time in restorative sleep—good for growth and development.

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TYPES OF SLEEP DISORDERS Much of the rest of the course talks about sleep disorders; however, we will talk briefly about these in this chapter as well. Sleep complaints are extremely common, with a third of individuals not getting enough regular sleep. Anxiety and depression will trigger sleep disorders in some people, while others are born with sleep problems. Poor sleep hygiene contributes to many sleep disorders as well.

Insomnias involve a difficulty falling asleep or staying asleep. It is the most common sleep disorder and can lead to sleep deprivation the next day. The symptoms of sleep deprivation can last for many days or years, depending on how severe the sleep disorder is. Insomnia can increase the risk of Alzheimer’s disease later in life and can lead to diabetes, heart disease, and obesity.

Circadian rhythm sleep-wake disorders happen to people who have a sleep-wake cycle that is not considered normal or healthy. These people sleep in the daytime and are awake at night, which is not typical of healthy sleep. Quality of life is affected and energy levels are low with difficulty concentrating. The most common circadian rhythm disorder is jet lag, which usually passes within a few days. Blind people can also have a circadian rhythm sleep disorder.

Hypersomnias are disorders of too much sleep. The patient cannot seem to get enough sleep and they sleep longer than 9 hours without feeling rested. Some of the problem can be due to sleep apnea, which interferes with adequate sleep. Some people can have idiopathic hypersomnia that is distinct from other causes of hypersomnia. Narcolepsy is a type of hypersomnia.

Parasomnias involve abnormal behaviors that happen during sleep. These can occur particularly during sleep transitions from one stage to the next. There is REM sleep disorder, where the person yells or moves violently in REM sleep. There is sleep paralysis, involving being unable to move when waking up or going to sleep.

Sleepwalking is another form of parasomnia. Some people can have “exploding head syndrome”, where hey hear a loud noise that jolts them awake as they are getting up or falling asleep. Bedwetting is a parasomnia of childhood that is usually outgrown.

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There are several sleep-related movement disorders that can happen in the middle of sleep or during transitions. Some of these include bruxism or the grinding of teeth in sleep, restless leg syndrome, and periodic limb movement disorder. These often result in sleep deprivation because the person has difficulty falling or staying asleep. These are somewhat rate but are seen in certain populations to a greater degree.

Sleep-related breathing disorders involve difficulty breathing at night or abnormal breathing patterns during sleep. Chronic snoring, central sleep apnea, and obstructive sleep apnea are three different types of sleep-related breathing disorders. Snoring may be simply a symptom of sleep apnea. The quality of sleep is poor so there are daytime difficulties and health problems related to poor sleep. Health problems seen in these disorders include a risk of stroke, heart attacks, high blood pressure, obesity, and low blood oxygen levels.

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