Narcolepsy is a sleep disorder that is often under-recognized and underdiagnosed. About 1 in every 2,000 people in North America and Europe suffer from this syndrome, which tends to be a lifelong phenomenon. The symptoms of narcolepsy can be terrifying at first and frustrating even after someone becomes used to them, but they never produce any serious illness. People with narcolepsy are usually healthy in all other respects. They have exactly the same natural life expectancy as those without it. No physical abnormality or tissue damage has ever been linked to this condition, either as a cause or as a consequence.
Men and women are equally likely to suffer from narcolepsy, and there is an increased risk for children of parents with the condition. It usually first appears in the teenage years, but it can come on at almost any age. Often the symptoms appear one by one, but in people aged over 20 it's more likely that several symptoms will appear at once. Symptoms may change over time in an individual, but there's no general tendency for them to get worse or better with age.
It is thought that people with narcolepsy have low levels of a brain protein called hypocretin (also known as orexin). This protein controls wakefulness and without it, people have a hard time staying awake. It is uncertain why some people have low levels of hypocretin, but scientists think this could be a result of the following: genetic mutations of a sleep gene, a family history, infections, brain injuries, contact with toxic substances (e.g., pesticides), and autoimmune diseases (e.g., rheumatoid arthritis).
One of the phases of sleep is called rapid eye movement (REM) sleep. In a normal sleep cycle, this usually occurs within 60 to 90 minutes of falling asleep. In a person with narcolepsy, REM sleep can occur anytime, even while a person is awake.
The low brain level of hypocretin is likely what causes a person with narcolepsy to enter rapid eye movement (REM) sleep in the daytime. This can be very concerning because a person's muscles in REM sleep are also paralyzed. Therefore, a person with narcolepsy could be standing up awake one moment and falling to the floor asleep the next.
Symptoms and Complications
There are a number of common symptoms of narcolepsy, but very few people have all of them.
The first and most important is excessive daytime sleepiness, so extreme that it becomes impossible to stay awake for more than a few moments no matter how hard the person tries, even if they're standing up. This may occur at any time, but is most likely to occur when the person is passive or bored - for example, in the classroom or at work. In a few cases, however, it occurs during physical exertion or stress, or when driving, eating, or speaking.
It's not difficult to rouse someone from such a state, and upon waking people may feel refreshed, but the tiredness may return very soon, forcing another bout of sleep. This may happen several times a day in the most severe cases. If someone with narcolepsy is left undisturbed, the sleep may last from a few minutes to a few hours.
Despite this, people with narcolepsy do not actually tend to sleep more hours in a day than people without the condition. This naturally implies that people with this condition get less sleep at night, and indeed many complain of unrefreshing nighttime sleep that's often interrupted by nightmares.
The other symptoms of narcolepsy (cataplexy, sleep paralysis, and Hypnagogic phenomena) are more rare, but most sufferers experience at least one of them from time to time. They all occur in fully conscious people and can be frightening if the person hasn't yet been diagnosed and doesn't know that they have narcolepsy.
In cataplexy, a person experiences emotionally triggered episodes of muscle weakness. The low muscle tone of REM sleep appears suddenly in a person who is fully awake at a time of strong emotion. Laughter, anger, fear, happiness, stress, or excitement can cause a person to go suddenly limp and drop to the ground.
Sleep paralysis occurs just before going to sleep or just after waking up. A temporary but complete paralysis prevents the person from moving for a few seconds. Sleep paralysis isn't actually that rare, especially in children, but it's only a sign of narcolepsy if one also experiences the primary symptom of suddenly falling asleep in the daytime.
Hypnagogic phenomena (hallucinations) also occur just before drifting off to sleep. Hypnopompic phenomena are hallucinations that occur just after waking, but are even rarer. Basically, they are vivid dreams that project into the waking period. Because they occur in people who aren't actually asleep, these dreams are sometimes called hallucinations.
As well as briefly falling asleep several times during the day, people with narcolepsy are prone to waking up several times a night. Sleep may be disrupted by insomnia, vivid dreams, sleep apnea and leg movements
There is one potential complication of narcolepsy, which is also a risk in other sleep disorders, and that's having an accident due to fatigue. The urge to sleep is so sudden and irresistible that it's more like passing out than going to sleep. It's been known to happen while operating a motor vehicle or heavy machinery. Similarly, people who don't sleep well at night may be below par in the daytime, whether they feel an urge to sleep or not. Even minor fatigue can impair judgement, making vehicles and heavy machinery dangerous. Controlling the symptoms of narcolepsy can go a long way towards preventing accidents.
Making the Diagnosis
There are many other causes of excessive daytime sleepiness. The most common are probably depression, sleep apnea (breathing problems during sleep), and sleep deprivation. None of these conditions, however, brings an urge to sleep that's as strong or as sudden as the urge felt by people with narcolepsy.
If your doctor suspects that you might have narcolepsy, they will likely refer you to a sleep clinic or specialist.
There are two tests that are be performed to diagnose narcolepsy. A polysomnogram (PSG) is an overnight sleep study which records brain and muscle activity, breathing and timing of REM sleep. It can rule out other conditions such as sleep apnea.
The second test is called the multiple-sleep latency test. The person spends the day at a sleep disorders clinic and is encouraged to take frequent small naps. Each time, they are hooked up to an electroencephalogram (EEG) and devices that measure eye movements and muscle tone. If someone tends to go into REM sleep as soon as they drop off, it's highly suggestive of narcolepsy.
A measurement of hypocretin levels in a person's cerebrospinal fluid (the fluid that surrounds the spinal cord) may also be done. A low hypocretin level helps to confirm the diagnosis of narcolepsy.
Specific changes in the brain of narcoleptic and cataplexic patients have been reported using various imaging techniques (MRI, SPECT, etc).
If the diagnosis of narcolepsy is made, the presence or absence of cataplexy determines which type of narcolepsy a person has. Type 1 narcolepsy is diagnosed if the person also has cataplexy; type 2 is diagnosed if they do not.
Treatment and Prevention
There's no cure for narcolepsy, but symptoms can be brought under control with medications. Medications called nervous system stimulants, which include amphetamines such as dextroamphetamine* and methylphenidate, are commonly used. Modafinil, another medication that helps to keep a person awake, may also be used.
Symptoms of cataplexy, sleep paralysis, and hypnagogic phenomena may be treated with tricyclic antidepressants (e.g., imipramine, desipramine, clomipramine) or selective serotonin reuptake inhibitors (e.g., fluoxetine, sertraline). Cataplexy may also be treated with sodium oxybate, but because of potential abuse, this medication is tightly regulated in Canada.
It's unlikely that medication treatment will completely eliminate all desire to sleep during the day. The best way to deal with this is to take 3 or 4 short, planned naps of about 20 minutes each. If treatment can't totally control symptoms, a person with narcolepsy may want to avoid work that involves long-distance driving or operating dangerous machinery for long periods.
Good sleep habits can also help with narcolepsy. Your doctor may suggest that you:
- go to sleep at the same time each day
- avoid having a TV in the bedroom
- have a warm bath or shower before going to bed
- avoid caffeine, alcohol, and nicotine before bed
- avoid medications that cause daytime drowsiness such as sedating antihistamines, sedatives and opioid pain relievers