Do you know that it is a serious medical condition? Narcolepsy affects an estimated 1 in 3,000 Americans. And living with the disease is very challenging.

You may have heard of narcolepsy before or recall a movie character hysterically falling asleep while walking. Our favorite TV dad, Homer Simpson, was diagnosed with narcolepsy in the premiere episode of the 27th season of The Simpsons after sleeping through a workplace fire that badly burned him. Homer used his doctor’s note to get out of doing household chores, driving Marge to file for legal separation. The episode is hilarious, but also highlights some of the real-life consequences of this sleep disorder.

We’ll look into the causes, diagnosis and treatment for this sleep disorder.

什么是嗜睡症？

Narcolepsy is a sleep disorder affecting an estimated 1 in 3,000 Americans; however, with increased education about the disease, the prevalence is expected to increase. It is a neurological disorder caused by the brain’s inability to regulate the sleep-wake cycle.

Our time asleep is divided into two main types of sleep:

NREM (non-rapid-eye-movement)

There are 3 stages of NREM sleep that make up 75% of our sleeping time. As we progress through these stages, our brain function decreases.

Stage 1: Light, transitionary phase between sleeping and wakefulness.

Stage 2: When you begin to drop into deeper sleep.

Stage 3: The deepest sleep stage. It is called slow-wave sleep because your brain activity moves up and down in synchronized waves. It is hard to wake someone from this type of sleep.

REM (rapid-eye-movement)

The brain is more active during REM sleep than NREM sleep; it can even rival our waking brain activity. Dreams occur during this sleep stage, your heart rate increases, your muscles become paralyzed, and your eyes twitch in various directions (hence the name).

For people with narcolepsy, sleep begins almost immediately with REM sleep and fragments of REM occur involuntarily throughout the waking hours. Due to the sudden transition into REM sleep, narcolepsy patients may experience paralysis and hallucinations while still awake (read more about that in the symptoms section below).

Despite the perception that people with narcolepsy are perpetually sleepy, they do not typically sleep more than the average person. Narcolepsy is considered a “state boundary” control abnormality. Narcolepsy patients sleep a normal amount but cannot control the timing of sleep.

There are two types of narcolepsy:

Type 1: Narcolepsy with cataplexy (we’ll explain cataplexy below).

Type 2: Narcolepsy without cataplexy.

What are the symptoms of narcolepsy?

Excessive daytime sleepiness: 嗜睡症最常见的症状是 EDS，即白天过度嗜睡，它与以下症状密切相关疲劳. EDS is a sensation of persistent drowsiness, even after a full night’s sleep, that results in impaired concentration and lack of energy. It can be punctuated by periods of “microsleep”, in which individuals may drift off for a short time without realizing it, and maybe without even interrupting their current task, such as driving or typing or other inappropriate times (see Francis inappropriately sleeping at his work space in the picture above).
Cataplexy: sudden loss of muscle tone, usually triggered by emotional stimuli such as laughter, surprise, or anger. It may involve all muscles and result in collapse. It may only affect certain muscle groups and result in slurred speech, buckling of the knees, or weakness in the arms. Consciousness is maintained throughout the episode but the patient is usually unable to speak.
Hypnagogic hallucinations: during transition from wakefulness to sleep, the patient has bizarre, often frightening dream-like experiences that incorporate his or her real environment.
Sleep paralysis: a temporary inability to move during sleep-wake transitions. Sleep paralysis may last for a few seconds to several minutes and may accompany hypnagogic hallucinations.
Fragmented nighttime sleep: waking up repeatedly through the night.

Who gets narcolepsy?

About 0.02% of African American, Caucasian, and Japanese individuals have narcolepsy. It is typically discovered in the the second and third decades of life (10-20s) and affects males and females equally. There may be combination of genetic or environmental factors that cause the disease.

How is narcolepsy diagnosed?

Like other sleep disorders, narcolepsy patients may suffer with the disease for years before being properly diagnosed.

Sleep history and records: Your doctor will ask you for a detailed sleep history. A part of the history involves filling out the 埃普沃思嗜睡量表, which uses a series of short questions to gauge your degree of sleepiness. You may be asked to keep a detailed diary of your sleep pattern for one to two weeks, so your doctor can compare how your sleep pattern and alertness are related.
Sleep study: The most common test for narcolepsy is an overnight polysomnogram (PSG, click here for more info on this test) followed by a daytime multiple sleep latency test (MSLT).IMPORTANT: Because the patient’s symptoms, like excessive daytime sleepiness, could be caused by another sleep disorder, such as sleep apnea, it is very important that the patient has an overnight sleep study the night before the daytime study. The overnight study will assess the quality of the night time sleep and may rule out other sleep disorders. If there is evidence of another sleep disorder during the overnight portion, the daytime MSLT may be canceled. Both tests may be repeated at a later date once the other sleep disorder is treated or ruled out as a cause of the EDS.
Blood test: A less common test looks at a genetic marker called the Narcolepsy-Associated Antigen, that is found in 90% to 95% of African American, Caucasian, and Japanese patients with narcolepsy who also have cataplexy (narcolepsy type 1), but only in 45% to 50% of patients with narcolepsy without cataplexy (narcolepsy type 2). Because about 25% of normal people have this gene, the absence of this gene is considered good evidence that the patient with cataplexy does NOT have narcolepsy; however, it’s absence doesn’t rule out narcolepsy without cataplexy (narcolepsy type 2).

How is narcolepsy treated?

Like sleep apnea, narcolepsy can be treated, but not cured.

Medications for narcolepsy include:

Stimulants: Drugs that stimulate the central nervous system to keep you awake during the day so that you can sleep at night.
SSRIs or SNRIs: These drugs suppress REM sleep and reduce symptoms of cataplexy, hypnagogic hallucinations and sleep paralysis.
Tricyclic antidepressants: These older antidepressants are effective for cataplexy.
Sodium oxybate (Xyrem): This medication is highly effective for cataplexy and improves nighttime sleep and may control daytime sleepiness. It has a short half-life and must be taken in two doses- one at bedtime and one four hours later. It is a highly controlled medication.

Lifestyle changes can also alleviate symptoms. Your doctor may recommend following a strict sleep timetable, which may include scheduled naps during the day, seeking counseling, and avoiding caffeine, alcohol, and large meals.

For more information on medications used to treat narcolepsy, visit the Mayo Clinic website 这里.

Has your doctor referred you for a test to rule out narcolepsy? Are you suffering from excessive daytime sleepiness and need a sleep study?

Request a sleep study

资料来源
http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/82026
https://sleepfoundation.org/sleep-disorders-problems/narcolepsy-and-sleep
http://www.sleepreviewmag.com/2014/04/narcolepsys-new-names/
http://theweek.com/articles/576595/simpsons-shows-why-narcolepsy-no-laughing-matter

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