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Non-24-hour sleep-wake disorder (N24) is a circadian rhythm sleep disorder in which an individual’s biological clock fails to synchronize to a 24-hour day. Instead of sleeping at roughly the same time every day, someone with N24 will typically find their sleep time gradually delaying by minutes to hours every day. They will sleep at later and later clock times until their sleep periods go all the way around the clock. (In extremely rare cases the sleep rhythm will gradually advance rather than delay.) Patients’ cycles of body temperature and hormone rhythms also follow a non-24-hour rhythm. Attempts to fight against this internal rhythm and sleep on a normal schedule result in severe and cumulative sleep deprivation.

N24 occurs in roughly 50% of completely blind people but also occurs in an unknown number of sighted people.

Kleine-Levin syndrome is a rare disorder characterized by the need for excessive amounts of sleep (hypersomnolence), (i.e., up to 20 hours a day); excessive food intake (compulsive hyperphagia); and behavioral changes such as an abnormally uninhibited sexual drive. The disorder primarily affects adolescent males. When awake, affected individuals may exhibit irritability, lack of energy (lethargy), and/or lack of emotions (apathy). They may also appear confused (disoriented) and experience hallucinations. Symptoms of Kleine-Levin syndrome are cyclical. An affected individual may go for weeks or months without experiencing symptoms. When present, symptoms may persist for days to weeks. In some cases, the symptoms associated with Kleine-Levin syndrome eventually disappear with advancing age. However, episodes may recur later during life.

The exact cause of Kleine-Levin syndrome is not known. However, researchers believe that in some cases, hereditary factors may cause some individuals to have a genetic predisposition to developing the disorder. It is thought that symptoms of Kleine-Levin syndrome may be related to malfunction of the portion of the brain that helps to regulate functions such as sleep, appetite, and body temperature (hypothalamus). Some researchers speculate that Kleine-Levin syndrome may be an autoimmune disorder.

Insomnia (also called insomnia disorder) is a common sleep problem that can affect your quality of life. People with insomnia have trouble falling asleep or staying asleep. They may wake up during the night or wake up too early the next morning.

Your sleep problems may come and go, or they may be ongoing.

• A short-term sleep problem is often linked to short-term stress. This short-term insomnia can last for days to weeks. It often gets better in less than a month.
• A chronic sleep problem is ongoing. This is called chronic insomnia. It is often a symptom of another health problem, such as depression or chronic pain. Chronic insomnia is less common than short-term sleep problems.

What causes insomnia?

There are many things that can cause sleep problems. Insomnia may be caused by:

• Stress. Stress can be caused by fear about a single event, such as giving a speech. Or you may have ongoing stress, such as worry about work or school.
• Depression, anxiety, and other mental or emotional conditions.
• Poor sleep habits, such as watching TV in bed or not having a regular bedtime schedule. If you have trouble sleeping, you may worry about being able to fall asleep. This can make the problem worse.
• Changes in your sleep habits or surroundings. This includes changes that happen where you sleep, such as noise, light, or sleeping in a different bed. It also includes changes in your sleep pattern, such as having jet lag or working a late shift.
• Other health problems, such as pain, breathing problems, and restless legs syndrome.
• Stimulants, such as tobacco and caffeine, as well as certain medicines, alcohol, and drugs.
• Lack of regular exercise.

What are the symptoms?

The symptoms of insomnia are different for each person. People with insomnia may:

• Have trouble falling asleep. This can mean lying in bed for up to an hour or more, tossing and turning, waiting to fall asleep.
• Wake up during the night and have trouble going back to sleep.
• Wake up too early in the morning.
• Feel tired when they wake up like they didn’t get enough sleep.
• Feel grouchy, sleepy, or anxious, and be unable to get things done during the daytime.

How is insomnia diagnosed?

Insomnia is not a disease, and no test can diagnose it. But when you can’t sleep well, it often has to do with some other cause. Your doctor will probably assess your current health and ask about any health problems you have had and any medicines you are taking.

Sometimes a doctor will do a physical exam, blood tests, and, in some cases, sleep studies to help find out if you have a health problem that may be causing insomnia.

Your doctor may also ask about your sleep history—how well you sleep, how long you sleep, your bedtime habits, and any unusual behaviors you may have. Your doctor may ask you to keep a sleep journal, which is a record of your sleep patterns, for a week or two. He or she may recommend a counselor if your symptoms point to a mental health problem, such as depression or anxiety.

How is it treated?

Treatment for insomnia focuses on the reason why you don’t sleep well. If you have a medical problem, such as chronic pain, or an emotional problem, such as stress, treating that problem may help you sleep better. You may be able to sleep better by making some small changes. It may help to:

• Go to bed at the same time each night.
• Get up at the same time each day.
• Avoid caffeine and alcohol for several hours before bedtime.
• Get regular exercise. Figure out what time of day works best for your sleep patterns.
• Avoid daytime naps.

Some people may need medicine for a while to help them fall asleep. Doctors often prescribe medicine for a short time if another treatment isn’t working. But medicine doesn’t work as well over time as lifestyle and behavior changes do. Sleep medicine can also become habit-forming. Medicine works best as a short-term treatment combined with lifestyle and behavior changes.

Your doctor may also recommend counseling, which can help you learn new habits that may help you sleep better.

Talk to your doctor about your sleep problems and any other health issues you may have. This is important because a lack of sleep can lead to depression, accidents, problems at work, marital and social problems, drinking more alcohol than usual, and poor health. Treatment may help you avoid these problems and feel better.

What are migraine headaches?

Migraines are painful, throbbing headaches that last from 4 to 72 hours. When you have a migraine, it may be so painful that you are not able to do your usual activities. But even though migraines make you feel bad, they don’t cause long-term damage.

Migraines are a health problem that can be treated. Talk to your doctor about your migraines.

What causes migraines?

Experts are not sure what causes migraines.

Migraines run in families, but it isn’t clear why some people get migraines and others don’t.

Some things can cause a migraine to start. These are called triggers. Your triggers may be different from someone else’s. Some common triggers include:

• Stress
• Not eating
• Poor sleep habits
• A change from your normal routine
• Red wine
• Monosodium glutamate (MSG)
• Strong odors
• Chocolate

What are the symptoms?

The main symptom of a migraine is a throbbing headache on one side of your head. You also may feel sick to your stomach and vomit. Activity, light, noise, or odors may make a migraine worse. The pain may move from one side of your head to the other, or you may feel it on both sides at the same time. Different people have different symptoms.

Some people have an aura before a migraine begins. When you have an aura, you may first see spots, wavy lines, or flashing lights. Your hands, arms, or face may tingle or feel numb. The aura usually starts about 30 minutes before a headache. But most people don’t have auras.

How are migraines diagnosed?

A doctor can usually tell if you have a migraine by asking about your symptoms and examining you. You probably will not need lab tests, but your doctor may order some if he or she thinks your symptoms are caused by another disease.

How are they treated?

You can’t cure migraines. But medicines and other treatments may help you feel better and limit how often you get migraines.

At first, your doctor may want you to try an over-the-counter pain medicine, such as acetaminophen, aspirin, ibuprofen, or naproxen. Brand names include Advil, Aleve, Bayer, and Tylenol. Some over-the-counter medicines (for example, Excedrin) combine acetaminophen, aspirin, and caffeine. Be safe with medicines. Read and follow all instructions on the label.

If these medicines don’t work, your doctor can prescribe stronger medicine to stop a migraine. Your doctor also may prescribe medicine to prevent migraines.

You may not be able to use some medicines if you are pregnant or have other health problems, such as heart problems.

If the first medicine doesn’t work, ask your doctor if you can try something else. It may take time to find what works best for you.

Some people also use other kinds of treatments, such as acupuncture. These may help reduce the pain or the number of migraines you have.

When you feel a migraine coming on:

• Stop what you are doing, and take your medicine. Don’t wait for a migraine to get worse. Take your medicine exactly as your doctor told you to.
• Rest in a quiet, dark room. Close your eyes, and try to relax or go to sleep. Don’t watch TV or read. Put a cold pack or cool cloth on the painful area.

Be careful when you use your migraine medicines. Taking them too often can cause you to get another headache when you stop taking the medicine. This is called a rebound headache. If you are taking headache medicine more than 2 days a week, or if you get more than 3 headaches a month, talk to your doctor.

Multiple sclerosis, often called MS, is a disease that affects the central nervous system—the brain and spinal cord. It can cause problems with muscle control and strength, vision, balance, feeling, and thinking.

Your nerve cells have a protective covering called myelin. Without myelin, the brain and spinal cord can’t communicate with the nerves in the rest of the body. MS gradually destroys myelin in patches throughout the brain and spinal cord, causing muscle weakness and other symptoms. These patches of damage are called lesions.

MS is different for each person. You may go through life with only minor problems. Or you may become seriously disabled. Most people are somewhere in between. Generally, MS follows one of four courses:

• Relapsing-remitting, where symptoms fade and then return off and on for many years.
• Secondary progressive, which at first follows a relapsing-remitting course and then becomes progressive. “Progressive” means it steadily gets worse.
• Primary progressive, where the disease is progressive from the start.
• Progressive relapsing, where the symptoms are progressive at first and are relapsing later.

What causes MS?

The exact cause is unknown, but most experts believe that MS is an autoimmune disease. In this kind of disease, the body’s defenses, called the immune system, mistakenly attack normal tissues. In MS, the immune system attacks the central nervous system—the brain and spinal cord.

Experts don’t know why MS happens to some people but not others. There may be a genetic link because the disease seems to run in families. Where you grew up may also play a role. MS is more common in those who grew up in colder regions that are farther away from the equator.

What are the symptoms?

Symptoms depend on which parts of the brain and spinal cord are damaged and how bad the damage is. Early symptoms may include:

• Muscle problems. You may feel weak and stiff, and your limbs may feel heavy. You may drag your leg when you walk.
• Vision problems. Your vision may be blurred or hazy. You may have eyeball pain (especially when you move your eyes), blindness, or double vision.
• Sensory problems. You may feel tingling, a pins-and-needles sensation, or numbness. You may feel a band of tightness around your trunk or limbs.
• Balance problems. You may feel lightheaded or dizzy or feel like you’re spinning.

How is MS diagnosed?

Diagnosing MS isn’t always easy. The first symptoms may be vague. And many of the symptoms can be caused by problems other than MS.

MS is not diagnosed unless a doctor can be sure that you have had at least two attacks affecting at least two different areas of your central nervous system. The doctor will examine you, ask you questions about your symptoms, and do some tests. An MRI is often used to confirm the diagnosis because the patches of damage (lesions) caused by MS attacks can be seen with this test.

How is it treated?

Medicines are used to treat MS:

• During a relapse, to make the attack shorter and less severe.
• Over a long period of time, to keep down the number of attacks and how severe they are and to slow the progression of the disease. (This is called disease-modifying therapy.)
• To control specific symptoms.

You may find it hard to decide when to start taking the drugs that slow the progression of MS. The drugs may not work for everyone, and they often have side effects. You and your doctor will decide together when you should start any of these drugs.

How do you live with MS?

There is no cure for MS. Treatment and self-care can help you maintain your quality of life.

Physical therapy, occupational therapy, and speech therapy can help you manage some physical problems caused by MS. You can also help yourself at home by eating balanced meals, getting regular exercise and rest, and learning to use your energy wisely.

Dealing with the physical and emotional demands of MS isn’t easy. If you feel overwhelmed, talk to your doctor. You may be depressed, which can be treated. And finding a support group where you can talk to other people who have MS can be very helpful.

Narcolepsy is a neurological sleep disorder characterized by chronic, excessive attacks of drowsiness during the day, sometimes called excessive daytime sleepiness (EDS). Attacks of drowsiness may persist for only a few seconds or several minutes. These episodes vary in frequency from a few incidents to several during a single day. Nighttime (nocturnal) sleep patterns may also be disrupted. Three additional symptoms often associated with narcolepsy are sudden extreme muscle weakness (cataplexy), a specific type of hallucination that occurs just before falling asleep or upon awakening, and brief episodes of paralysis while waking up. Narcolepsy also may be associated with “automatic behavior”, i.e. doing something automatically without any memory afterward. The incidence of narcolepsy is approximately 1 in 2,000 and most researchers believe that the disorder remains undiagnosed or misdiagnosed in many cases.

There is increasing evidence that narcolepsy is an autoimmune disorder. Autoimmune disorders are caused when the body’s immune system mistakenly attacks healthy tissue or cells. In narcolepsy, the immune system destroys certain brain cells that produce a peptide called hypocretin. Hypocretin impacts on many brain functions, but the details of its actions are not yet understood. Why the immune system attacks healthy cells in narcolepsy is unknown and additional environmental and genetic factors may play a role in the development of the disorder.

Parasomnias are undesirable physical activities that occur during sleep involving skeletal muscle activity, nervous system changes, or both. Night terrors and sleepwalking are two types of parasomnias. Sleep can be hard for people who experience parasomnias. While “asleep,” a person with parasomnia may walk, scream, rearrange furniture, eat odd foods, or pick up a weapon.

Parasomnia can cause odd, distressing, and sometimes dangerous nighttime activities. These disorders have medically explainable causes and usually are treatable.

For most people, dreaming is purely a “mental” activity: dreams occur in the mind while the body is at rest. But people who suffer from REM sleep behavior disorder (RBD) act out their dreams. They physically move limbs or even get up and engage in activities associated with waking. Some engage in sleep talking, shouting, screaming, hitting or punching. Some even fly out of bed while sleeping! RBD is usually noticed when it causes danger to the sleeping person, their bed partner, or others they encounter. Sometimes ill effects such as injury to self or bed partner sustained while asleep trigger a diagnosis of RBD. The good news is that RBD can usually be treated successfully.

What we call “sleep” involves transitions between three different states: wakefulness, rapid eye movement (REM) sleep, which is associated with dreaming, and non-rapid eye movement (N-REM) sleep. There are a variety of characteristics that define each state but to understand REM sleep behavior disorder it is important to know that it occurs during REM sleep. During this state, the electrical activity of the brain, as recorded by an electroencephalogram, looks similar to the electrical activity that occurs during waking. Although neurons in the brain during REM sleep are functioning much as they do during waking, REM sleep is also characterized by temporary muscle paralysis.

In some sleep disorders such as narcolepsy and parasomnias, like REM sleep behavior disorder, the distinctions between these different states breaks down; characteristics of one state carry over or “invade” the others. Sleep researchers believe that neurological “barriers” that separate the states don’t function properly, though the cause of such occurrences is not entirely understood.

Restless legs syndrome (RLS) is a disorder related to sensation and movement. People with restless legs syndrome have an unpleasant feeling or sensation in parts of their bodies when they lie down to sleep. Most people also have a very strong urge to move, and moving sometimes makes them feel better. But all this movement makes it hard or impossible to get enough sleep.

Restless legs syndrome usually affects the legs. But it can cause unpleasant feelings in the arms, torso, or even a phantom limb (the part of a limb that has been amputated).

When you don’t get enough sleep, you may start to have problems getting things done during the day because you’re so tired. You may also be sleepy or have trouble concentrating. So it’s important to see your doctor and get help to manage your symptoms.

What causes restless legs syndrome?

Usually, there isn’t a clear reason for restless legs. The problem often runs in families. Sometimes there is a clear cause, like not getting enough iron. If that’s the case, treating the cause may solve the problem.

Women sometimes get restless legs while they are pregnant.

Other problems that are sometimes linked to restless legs syndrome include kidney failure, rheumatoid arthritis, diabetes, nerve damage, anemia, and Parkinson’s disease. But most people who seek treatment do not have any of these other problems.

What are the symptoms?

Restless legs syndrome makes you feel like you must move a part of your body, usually your legs. These feelings are often described as tingling, “pins and needles,” prickling, pulling, or crawling.

Moving will usually make you feel better, at least for a short time. This problem usually happens at night when you are trying to relax or go to sleep.

After you fall asleep, your legs or arms may begin to jerk or move. These movements are called periodic limb movements. They can wake you from sleep, which adds to your being overtired. Although periodic limb movement is considered a separate condition, it often happens to people who have restless legs syndrome.

How is restless legs syndrome diagnosed?

One of the hardest things about having restless legs syndrome is getting to the diagnosis. Often doctors don’t ask about sleep or don’t ask about the symptoms of restless legs. If you’re not sleeping well, or if you think you may have restless legs syndrome, tell your doctor.

Your doctor will talk with you about your symptoms to make sure that the feelings you describe are typical of restless legs syndrome and are not caused by some other problem.

You may have blood tests to rule out other problems that could be causing your symptoms. In some cases, the doctor may order tests of your nerves to be sure there is no nerve damage. Your doctor may also order a sleep study called a polysomnography. This test records how often your legs jerk or move while you sleep.

How is it treated?

If your symptoms are mild, a few lifestyle changes may be enough to control your symptoms. Some changes that may help:

• Avoid tobacco, alcohol, and caffeine.
• Keep your bedroom cool, quiet, and comfortable, and use it only for sleeping, not for watching TV.
• Get regular exercise.
• Massage the leg or the arm, or use heat or ice packs.

When symptoms are more severe, medicines may help control the urge to move and help you sleep. There are different types of medicine, and you may have to try a few to find the one that works best.

Sleep apnea means that your breathing often is blocked or partly blocked during sleep. The problem can be mild to severe, based on how often your lungs don’t get enough air. This may happen from 5 to more than 50 times an hour.

This topic focuses on obstructive sleep apnea, which is the most common type.

A less common type of apnea called central sleep apnea can occur in people who have had a stroke, have heart failure, or have a brain tumor or infection. Even though this topic isn’t about central sleep apnea, some of the treatments discussed here may also help treat it. Talk with your doctor to find out more about central sleep apnea.

What causes obstructive sleep apnea?

Blocked or narrowed airways in your nose, mouth, or throat can cause sleep apnea. Your airways can become blocked when your throat muscles and tongue relax during sleep.

Sleep apnea can also occur if you have large tonsils or adenoids. During the day, when you are awake and standing up, these may not cause problems. But when you lie down at night, they can press down on your airway, narrowing it and causing sleep apnea. Sleep apnea can also occur if you have a problem with your jawbone.

In children, the main cause of sleep apnea is large tonsils or adenoids.

Sleep apnea is more likely to occur if you are overweight, use certain medicines or alcohol before bed, or sleep on your back.

What are the symptoms?

The main symptoms of sleep apnea that you may notice are:

• Not feeling rested after a night’s sleep.
• Feeling sleepy during the day.
• Waking up with a headache.

Your bed partner may notice that while you sleep:

• You stop breathing.
• You often snore loudly.
• You gasp or choke.
• You toss and turn.

Children who have sleep apnea:

• Nearly always snores.
• May be hyperactive or have problems paying attention during the day.
• May be restless during sleep and wake up often. They also may have problems with bed-wetting.

But children may not seem very sleepy during the day (a key symptom in adults). The only symptom of sleep apnea in some children may be that they do not grow as quickly as most children their age.

Can sleep apnea cause other problems?

Having sleep apnea can lead to serious problems such as:

• High blood pressure.
• High blood pressure in your lungs.
• An abnormal heart rhythm, heart failure, coronary artery disease (CAD), or stroke.
• Depression.
• Diabetes.

If you have sleep apnea, you also may not be sleeping as well as you could. If you feel sleepy during the day and this gets in the way of the normal things you do (like work, school, or driving), it’s important to talk to your doctor. Be safe. Do not drive while you are drowsy.

How is sleep apnea diagnosed?

Your doctor will probably examine you and ask about your past health. He or she may also ask you or your sleep partner about your snoring and sleep behavior and how tired you feel during the day.

Your doctor may suggest a sleep study. A sleep study usually takes place at a sleep center, where you will spend the night. Sleep studies find out how often you stop breathing or have too little air flowing into your lungs during sleep. They also find out how much oxygen you have in your blood during sleep. You may have blood tests and X-rays.

How is it treated?

You may be able to treat mild sleep apnea by making changes in how you live and the way you sleep. For example:

• Lose weight if you are overweight.
• Sleep on your side and not your back.
• Avoid alcohol and medicines such as sedatives before bed.

If lifestyle changes don’t help sleep apnea, you may be able to use an oral breathing device or other types of devices. These devices help keep your airways open while you sleep.

Sleep apnea is often treated with a machine that helps you breathe while you sleep. This treatment is called continuous positive airway pressure, or CPAP (say “SEE-pap”). Sometimes medicine that helps you stay awake during the day may be used along with CPAP. If your tonsils, adenoids, uvula, or other tissues are blocking your airway, your doctor may suggest surgery to open your airway.

This topic is about simple snoring. If you stop breathing, choke, or gasp during sleep, you may have a problem called sleep apnea, which can be serious. For more information, see the topic Sleep Apnea.

What is snoring?

You snore when the flow of air from your mouth or nose to your lungs makes the tissues of your throat vibrate when you sleep. This can make a loud, raspy noise. Loud snoring can make it hard for you and your partner to get a good night’s sleep.

You may not know that you snore. Your bed partner may notice the snoring and that you sleep with your mouth open. If snoring keeps you or your bed partner from getting a good night’s sleep, one or both of you may feel tired during the day.

Snoring may point to other medical problems, such as obstructive sleep apnea. Sleep apnea can be a serious problem because you stop breathing at times during sleep. So if you snore often, talk to your doctor about it.

Snoring is more common in men than in women.

What causes snoring?

When you sleep, the muscles in the back of the roof of your mouth (soft palate), tongue, and throat relax. If they relax too much, they narrow or block your airway. As you breathe, your soft palate and uvula vibrate and knock against the back of your throat. This causes the sounds you hear during snoring.

The tonsils and adenoids may also vibrate. The narrower the airway is, the more the tissue vibrates, and the louder the snoring is.

How is it treated?

You may be able to treat snoring by making changes in your lifestyle and in the way you prepare for sleep. For example:

• Lose weight if you are overweight.
• Quit smoking.
• Sleep on your side and not your back.
• Limit your use of alcohol and medicines such as sedatives before you go to bed.
• If a stuffy nose makes your snoring worse, use decongestants or nasal corticosteroid sprays to help you breathe.
• Try using devices that you attach to the outside of your nose to help with breathing while you sleep. These include nasal strips and nasal disks.
• When you sleep, use a device in your mouth that helps you breathe easier. This device pushes your tongue and jaw forward to improve airflow.

If these treatments don’t work, you may be able to use a machine that helps you breathe while you sleep. This treatment is called continuous positive airway pressure, or CPAP (say “SEE-pap”). In rare cases, your doctor may suggest surgery to open your airway.

Snoring isn’t always considered a medical problem, so find out if your insurance covers the cost of treatment.

Non-REM (NREM) sleep

Non–rapid eye movement (NREM) sleep has 3 stages:

• Stage N1 occurs right after you fall asleep and is very short (usually less than 10 minutes). It involves light sleep from which you can be awakened easily.
• Stage N2 lasts from about 30 to 60 minutes. During this stage, your muscles become more relaxed and you may begin to have slow-wave (delta) brain activity.
• Stage N3 is deep sleep and lasts about 20 to 40 minutes. During this stage, delta brain activity increases and a person may have some body movements. It is very hard to wake up someone in stage N3.

REM (R) sleep

Rapid eye movement sleep is deeper than non-REM sleep. During REM sleep:

• The eyes and eyelids flutter.
• Breathing becomes irregular. During REM sleep, it is normal to have short episodes when breathing stops (apnea).

You do most of your dreaming during REM sleep. But your brain paralyzes your muscles so you do not act out the dreams.

During sleep, a person usually progresses through the 3 stages of non-REM sleep before entering REM sleep. This takes about 1 to 2 hours after falling asleep. The cycle is repeated three to four times each night. An adult spends more time in NREM sleep than in REM sleep. An infant usually spends about half of the sleeping time in NREM and half in REM stages.