Sleep Disorders: An Overview

Table of Contents

It’s estimated that as many as 70 million people in the United States have a sleep disorder. Sleep disorders are a broad category of medical conditions that negatively affect sleep. Understanding sleep disorders can help people minimize the consequences of poor sleep, which can include diminished quality of life and an increased risk of developing health issues. We discuss the many types of sleep disorders, including their symptoms and causes. We also cover some of the ways sleep disorders are diagnosed and treated and steps you can take to get a better night’s sleep.

Sleep disorders are conditions that disrupt healthy sleep and also cause daytime symptoms. Sleep disorders can affect when you are able to fall asleep, how much sleep you get, and the quality of your sleep.

Classification systems are used to organize different types of sleep disorders. These systems help researchers study sleep issues and provide a framework that helps doctors diagnose and treat sleep disorders. They also help to determine when a person’s symptoms may be normal and when they require treatment.

The most widely used system for classifying sleep disorders is produced by the American Academy for Sleep Medicine (AASM). The third edition of the International Classification of Sleep Disorders (ICSD-3) describes 60 sleep disorders, divided into seven categories. These main categories include:

• Insomnia
• Sleep-related breathing disorders
• Circadian rhythm sleep-wake disorders
• Central disorders of hypersomnolence
• Parasomnias
• Sleep-related movement disorders
• Other sleep disorders

Insomnia

Affecting as many as two-thirds of adults, insomnia is the most widespread sleep disorder in the United States. In fact, insomnia is one of the most common reasons why adults look for medical care.

Insomnia occurs when people who have plenty of opportunities for rest find themselves unable to fall asleep, waking during the night, or waking up earlier than they’d like. Insomnia may be diagnosed as short-term or chronic.

• Short-term insomnia disorder: Short-term insomnia describes fleeting symptoms of sleeplessness that last for less than three months. Often related to stress, short-term insomnia can sometimes develop into a chronic condition.
• Chronic insomnia disorder: When the symptoms of insomnia are more persistent — happening at least three days a week for three months or more — a doctor may diagnose chronic insomnia.

Sleep-Related Breathing Disorders

As the name implies, sleep-related breathing disorders are a category of sleep disorders in which a person experiences abnormal breathing during sleep. Researchers estimate that between 2% and 4% of adults have a sleep-related breathing disorder.

• Obstructive sleep apnea disorders: Obstructive sleep apnea describes repeated episodes in which breathing becomes shallow or stops during sleep. Episodes are caused by a blockage in the airway.
• Central sleep apnea syndromes: Central sleep apnea also involves periods of shallow or paused breathing. Unlike obstructive sleep apnea, though, this condition is caused by problems with the signals that are sent from the brain to control breathing.
• Sleep-related hypoventilation disorders: In these disorders, a sleeper doesn’t breathe quickly or deeply enough to meet the body’s demands. People with sleep-related hypoventilation disorders have high carbon dioxide and low oxygen levels throughout the night.
• Sleep-related hypoxemia disorder: Hypoxemia describes low levels of oxygen in the blood. While hypoxemia during sleep is often caused by hypoventilation or another sleep disorder, this is not always the case.

Each of these four groups can be further broken down based on the underlying cause of abnormal breathing. Additionally, many people with abnormal nighttime breathing meet the criteria for multiple sleep-related breathing disorders.

Circadian Rhythm Sleep-Wake Disorders

Circadian rhythm sleep-wake disorders are conditions in which a person’s circadian rhythm is disrupted or out of sync with their surroundings. Circadian rhythms are near 24-hour cycles in the body that control the timing of various processes, including when a person sleeps and wakes up.

As a group, these disorders affect less than 1% of the general population, though they occur more frequently in adolescents, young adults, and people with mental health conditions.

• Delayed sleep-wake phase disorder: Common in adolescents, people with delayed sleep-wake phase disorder have a sleep schedule that is later than what is typical. This delay in their circadian rhythm can cause issues in their work, school, or personal lives because they might not be able to get enough sleep to function well.
• Advanced sleep-wake phase disorder: In advanced sleep-wake disorder, a person’s circadian rhythm causes them to fall asleep and wake up earlier than what is typical. This disorder is most often diagnosed in older adults.
• Irregular sleep-wake rhythm disorder: People with irregular sleep-wake rhythm disorder don’t have a defined circadian rhythm, leaving them feeling sleepy or having symptoms of insomnia at different points in the day.
• Non-24-hour sleep-wake rhythm disorder: Non-24-hour sleep-wake rhythm disorder is characterized by a constantly shifting circadian rhythm, so a person’s sleep-wake cycle changes slightly each day. This sleep disorder mostly affects people who are blind, but can also affect sighted individuals.
• Shift work sleep disorder: Shift workers have a work schedule that falls outside of the typical 7 a.m. to 6 p.m. time frame. When people are unable to adjust their sleep habits to these work schedules, they may develop shift work sleep disorder. This disorder can cause sleep issues as well as sleepiness and other impairments at work.
• Jet lag disorder: Jet lag occurs after traveling across time zones, which causes the circadian rhythm to be out of sync with the time of day at the destination. Jet lag can cause excessive tiredness during the day and challenges falling asleep at the appropriate time in the evening.

Central Disorders of Hypersomnolence

Central disorders of hypersomnolence are sleep disorders in which the main symptom is significant tiredness or dozing off during the day. In people with one of these sleep disorders, daytime sleepiness is not related to a poor night’s sleep, out of sync circadian rhythms, or another sleep disorder.

• Narcolepsy: Narcolepsy is a disorder involving excessive daytime sleepiness that persists despite getting enough rest. People with narcolepsy may also doze off uncontrollably and have episodes in which they temporarily lose control over their muscles, in addition to other symptoms.
• Hypersomnia: Hypersomnia is a medical term for feeling excessively tired during the day or sleeping longer than needed at night. Hypersomnia can be caused by a mental or physical health condition, can be due to a medication or other substance, or it can exist with no detectable cause.
• Kleine-Levin syndrome: This uncommon sleep disorder involves periods of intense sleepiness, during which a person has changes in their thoughts, feelings, or behavior. Each episode can last anywhere from two days to five weeks.
• Insufficient sleep syndrome: When daytime sleepiness persists because a person chooses not to spend enough time in bed or get the needed amount of sleep, the condition may be diagnosed as insufficient sleep syndrome.

There is significant variation in how often each of these sleep disorders is diagnosed. For example, the most common form of narcolepsy affects roughly 1 in 2,000 people, while Kleine-Levin syndrome only affects between 1 and 5 people out of every 1,000,000.

Parasomnias

Parasomnias involve certain movements, behaviors, feelings, or perceptions that happen as a person is falling asleep, during sleep, or while they are waking up. Sleep is divided into two phases, non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep, and parasomnias are categorized based on the phase of sleep in which the experience occurs.

Many parasomnias occur as a person is waking up from deep, NREM sleep. Also called disorders of arousal, these parasomnias affect fewer than 3% of adults.

• Confusional arousals: In this parasomnia, a person repeatedly wakes up from sleep feeling confused or disoriented. Episodes may last from several minutes to multiple hours.
• Sleepwalking: Sleepwalking is a parasomnia in which a person gets out of bed and engages in activities like walking, talking, cleaning, and driving. After sleepwalking, people may have no recollection of or only partially remember the experience.
• Sleep terrors: Sleep terrors involve sudden and intense fear and confusion. Usually lasting for a few minutes, a person experiencing sleep terrors may sit up, scream, or act violently.
• Sleep-related eating disorder: A person may be diagnosed with a sleep-related eating disorder if they repeatedly eat while partially awake. To be diagnosed with this parasomnia, a person must eat abnormally, ingest toxic or inedible substances, harm themselves while in search of food, or have health effects related to nighttime eating.

Parasomnias can also occur during REM sleep, which is a period of increased brain activity when most dreams occur.

• Rapid eye movement sleep behavior disorder: People with this sleep disorder act out their dreams by making sounds or moving during sleep. This parasomnia can possibly put the sleeper or their bed partner at risk of injury.
• Recurrent isolated sleep paralysis: Sleep paralysis involves being unable to move the body for a short time when falling asleep or while waking up. Hallucinations may also occur during these episodes. If these episodes aren’t related to another sleep disorder, they may be diagnosed as recurrent isolated sleep paralysis.
• Nightmare disorder: While most people experience nightmares, few actually have nightmare disorder. Nightmare disorder involves seriously distressing dreams that lead to changes in mood, behavior, or challenges with daily activities. People with nightmare disorder remember their frightening dreams vividly after waking up.

Rapid eye movement sleep behavior disorder occurs in less than 1% of the population, while as many as 40% of people have at least one episode of sleep paralysis. Up to 8% of people experience recurrent nightmares.

Several additional parasomnias aren’t associated with a specific phase of sleep and may occur during NREM or REM sleep.

• Exploding head syndrome: People with exploding head syndrome hear a loud noise or feel as if their head is exploding as they fall asleep or while they are waking up. While painless, these imagined sensations may be frightening and are often described as a bomb, cymbals, or a loud bang.
• Sleep-related hallucinations: Hallucinations involve perceiving experiences that aren’t really happening. If hallucinations occur as a person is falling asleep or waking up, and can’t be attributed to another sleep disorder, they may be diagnosed as sleep-related hallucinations.
• Sleep enuresis: Sleep enuresis is a parasomnia in which a person older than 5 years of age urinates during sleep. For this diagnosis to apply, bedwetting must occur at least twice a week for three months or longer.

Sleep-Related Movement Disorders

Sleep-related movement disorders are sleep disorders involving disturbed rest or daytime symptoms caused by repetitive movements during sleep.

• Periodic limb movement disorder: Periodic limb movement disorder is marked by repetitive movements of the limbs during sleep that cause sleep issues, fatigue, or other daytime impairments.
• Restless legs syndrome: A person with restless legs syndrome feels an impulse to move their legs while resting that can make it difficult to fall asleep. These impulses may temporarily go away after movement, only to return shortly after. Some people describe experiencing a tingling or itching sensation in their legs.
• Sleep-related leg cramps: Also called nocturnal leg cramps, people with this sleep disorder have sudden cramps in their calf, foot, or other lower extremities. These cramps occur while a person is in bed, either awake or asleep.
• Sleep-related bruxism: Bruxism is a medical term for teeth grinding, which is when a person forcefully rubs their teeth against one another. Most teeth grinding occurs during sleep, and sleep-related bruxism may be diagnosed if clenching and grinding lead to tooth damage or other daytime symptoms.
• Sleep-related rhythmic movement disorder: While some repetitive movements are considered normal during sleep, like baby head banging, they may be diagnosed as a sleep disorder if the movements interrupt sleep or cause injury.
• Benign sleep myoclonus of infancy: Benign sleep myoclonus of infancy is a sleep disorder that can affect babies younger than 6 months old. Infants with this disorder experience twitching or jerking during sleep that can involve individual body parts or the entire body. It’s not harmful and typically resolves on its own.
• Propriospinal myoclonus at sleep onset: This sleep disorder involves twitches or jerks that occur on the edges of sleep, most often as a person is dozing off. These movements can make it hard to fall asleep, but resolve once a person is fully asleep or fully awake.

Other Sleep Disorders

This category, referred to as other sleep disorders, includes sleep issues that don’t fit within other categories or that span multiple categories. This diagnosis may also be used when there is limited research regarding an emerging sleep disorder.

While in some cases the cause of a sleep disorder is clear, often the development of a sleep disorder is influenced by a combination of risk factors. In other cases, the cause of a sleep disorder may be unknown.

Factors that increase the risk of certain sleep disorders include:

• Underlying medical conditions
• Mental health conditions
• Medications or other substances
• Genetics
• Environmental stressors

There is a wide range of symptoms among sleep disorders. They vary from one disorder to the next, and two people with the same sleep disorder may experience different symptoms. Common symptoms of sleep disorders include:

• Trouble falling asleep
• Waking up often during the night
• Sleeping at inappropriate times
• Daytime fatigue or sleepiness
• Changes in mood, attention, motivation, or concentration
• Accidents and mistakes
• Snoring, gasping for breath, or pauses in breathing during sleep
• Auditory, visual, or tactile hallucinations
• Sudden weakness in the muscles
• Uncomfortable sensations in the legs or limb movements
• Feeling unable to move immediately after waking up

Anyone concerned about sleep disorders or experiencing symptoms should speak with their doctor.

To diagnose a sleep disorder, a doctor will often start by reviewing a person’s symptoms and medical history, asking about their use of medications and other substances, and conducting a physical exam. Other tests help doctors make a diagnosis or rule out various other conditions.

• Questionnaires: Doctors may have people fill out specially designed forms to measure sleepiness, fatigue, and other symptoms.
• Sleep journal: To help understand how sleep habits and symptoms change over time, a doctor may recommend that people keep a sleep journal. Also called a sleep diary or sleep log, this record is often collected over several weeks to identify trends or changes.
• Actigraphy: Actigraphy provides doctors with information about daytime activities as well as sleep. This device that’s used, called an accelerometer, is worn on the wrist and measures movement throughout the day and night.
• Sleep study: A sleep study uses devices to monitor and collect data about various body functions during sleep. A type of sleep study called polysomnography involves staying in a sleep lab overnight, while some sleep apnea tests can be performed at home.
• Multiple sleep latency testing: Conducted the day after polysomnography, a multiple sleep latency test involves taking several naps in a sleep lab. During this time, measurements can be taken to assess how long it takes to fall asleep and the amount of time spent in each phase of sleep.
• Other tests: Doctors may also recommend blood work, imaging, and other tests to rule out other causes of a person’s symptoms.

Treatment for sleep disorders depends on a person’s individual circumstances and the type of sleep disorder diagnosed. Treatments may include medical interventions and lifestyle changes.

• Cognitive behavioral therapy for insomnia (CBT-I): Often the first approach to treating insomnia, cognitive behavioral therapy for insomnia addresses the thoughts, feelings, and actions that interfere with healthy sleep.
• Positive airway pressure therapy: Positive airway pressure is a treatment used for several sleep-related breathing disorders. This treatment involves the use of a machine that pumps pressurized air through the airway during sleep.
• Bright light therapy: Exposure to bright light at strategic times can shift a person’s circadian rhythm and may be an effective treatment for some people with circadian rhythm sleep-wake disorders.
• Oral devices: Devices worn in the mouth may be used to treat several sleep disorders, including obstructive sleep apnea and sleep-related bruxism.
• Surgery: Surgery may be used to manage sleep disorders including obstructive and central sleep apnea.
• Medications: Doctors may prescribe medications to help with sleep or to address an underlying medical condition that is contributing to sleep problems. Depending on the sleep disorder, medicines may be used alone, in combination with other approaches, or only after other treatments are unsuccessful.

Sleep hygiene refers to habits that support healthy sleep. Improving sleep hygiene is an effective treatment for several sleep disorders. Steps to improve sleep hygiene include:

• Getting seven to nine hours of sleep every night
• Keeping a consistent schedule of bedtimes and wake times
• Getting physical activity every day
• Reducing caffeine, nicotine, and alcohol use, especially a few hours before bedtime
• Removing lights, computers, and TVs from the bedroom
• Creating a comfortable sleep environment

About The Author

Alison Deshong

Staff Writer, Product Testing Team

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Alison is a health writer with ample experience reading and interpreting academic, peer-reviewed research. Based in San Diego, she is published in the journal PLOS Genetics and the Journal of Biological Chemistry and has been a copywriter for SmartBug media. With a master’s degree in biochemistry from the University of California, Davis, she has nearly a decade of academic research experience in life sciences. She enjoys helping people cut through the noise to understand the bigger picture about sleep and health. Alison likes to stay active with rock climbing, hiking, and walking her dog.

• POSITION: Stomach sleeper
• TEMPERATURE: Neutral Sleeper
• CHRONOTYPE: Bear

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