Narcolepsy is an under-diagnosed, disabling disorder of the brain that affects the control of sleep and wakefulness.
Individuals with narcolepsy experience chronic daytime sleepiness, abnormal rapid eye movement sleep, and cataplexy (brief attacks of muscle weakness and tone triggered by strong emotions).
Narcolepsy can range in severity from mild to severe, and negatively impact one's social activities, school, work, and overall health and well-being.
Narcolepsy typically begins in the teen years, or early twenties and thirties. It affects 3 million people worldwide. The exact cause of narcolepsy is unknown, although researchers believe it to be an inherited autoimmune disease that leads to a deficiency in hypocretin, a chemical the brain needs to stay awake.
Although there is no cure for narcolepsy, it can be managed with lifestyle modifications and medication therapy.
Contents of this article:
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on narcolepsy
Here are some key points about narcolepsy. More detail and supporting information is in the main article.
- 40 million Americans each year suffer from chronic, long-term sleep disorders.
- Although highly prevalent, common sleep disorders are infrequently identified by primary care providers.
- Narcolepsy is the second leading cause of excessive daytime sleepiness after obstructive sleep apnea.
- The average time from the onset of narcolepsy to diagnosis is about 10 years.
- Symptoms typically begin to occur between the ages of 10 and 30.
- Narcolepsy is caused by the loss of the two brain chemicals called hypocretins.
- Researchers have identified a gene that is linked to narcolepsy.
- The main symptoms of narcolepsy are excessive daytime sleepiness and abnormal rapid eye movement (REM) sleep.
- The medical community first recognized narcolepsy in the late 19th century.
- Approximately 1:2000 people have the disorder.
- It is equally common in men and women.
- Narcolepsy can be treated with medications and adjustments to lifestyle.
What is narcolepsy?
Narcolepsy is a considered a hypersomnia or a sleep disorder characterized by excessive daytime sleepiness.
Many cases of narcolepsy are caused by a lack of the brain chemical orexin (also known as hypocretin), which regulates sleep.
In a typical sleep cycle, we enter the early stage of sleep, followed by deeper sleep stages for 90 minutes where finally REM sleep occurs.
For people with narcolepsy, REM sleep occurs almost immediately in the sleep cycle, and intermittently during the waking hours. It is in REM sleep that dreams and muscle paralysis occur.
Causes of narcolepsy
Nerve-signaling chemicals called neurotransmitters control whether we are asleep or awake by acting on different groups of nerve cells, or neurons in the brain.
Narcolepsy results from the loss of the neurotransmitters known as hypocretin (also called orexin). These neurotransmitters are made in the hypothalamus region of the brain and are necessary to maintain wakefulness.
When hypocretin is not available, the brain allows REM sleep phenomena to intrude into normal waking periods. As a result, people with narcolepsy suffer from excessive daytime sleepiness, and nighttime sleeping problems.
Narcolepsy is believed to be an autoimmune disease with a genetic predisposition. An autoimmune disease is a disorder where the body's immune system mistakenly attacks itself and fights off healthy cells as if they were foreign invaders. Some commonly recognized autoimmune diseases are rheumatoid arthritis, type 1 diabetes, and celiac disease.
Symptoms of narcolepsy
The hallmark symptom of narcolepsy is excessive daytime sleepiness (EDS). Additional symptoms may include cataplexy, hypnagogic hallucinations, and sleep paralysis.
In most cases, excessive daytime sleepiness is the first sign of narcolepsy. This can have a significant impact on everyday life.
Excessive daytime sleepiness (EDS) is a persistent background feeling of sleepiness with a tendency to doze off at intervals throughout the day, often at inappropriate times (sleep attacks).
EDS can lead to brain fog, poor concentration, decreased energy, memory lapses, exhaustion, and a depressed mood.
Cataplexy is a sudden muscle weakness in the face, neck, and knees. Some people have only mild weakness such as head or jaw drop, while others will completely collapse to the ground. These episodes are generally triggered by strong emotions like surprise, laughter, or anger. The weakness is temporary, lasting two minutes or less.
Hypnogogic hallucinations are vivid, often frightening sensory hallucinations that occur while falling asleep. These could be caused by the blend of wakefulness and the dreaming that occurs with REM-sleep.
Sleep paralysis is a brief inability to move or speak while falling asleep or waking up. These episodes typically last a few seconds to several minutes. After the episode's end, people rapidly recover their full capacity to move and speak.
On the next page we look at tests and diagnosis of narcolepsy and the available treatment options for the condition.