Narcolepsy is a chronic neurological disorder characterized by excessive daytime sleepiness, sudden loss of muscle tone (cataplexy), and disturbed sleep patterns, including intense hallucinations and sleep paralysis. It is often caused by a deficiency of a neurotransmitter called hypocretin (orexin). Treatment includes medications and lifestyle adjustments to manage symptoms and improve quality of life. The assessment of the Polygenic Risk Score for narcolepsy is based on the examination of 20 gene polymorphisms.
Genetic testing for narcolepsy is included along with 15 other diseases in the Genetic Screening for Diseases of the Nervous System, Polygenic Risk Score.
Causes and non-genetic risk factors
The cause of narcolepsy is not fully understood. However, studies indicate that it may result from a combination of factors that trigger a lack of hypocretin, a natural chemical that promotes wakefulness and regulates REM sleep in narcolepsy accompanied by cataplexy. Some of these currently suggested causes include the following:
- Autoimmune disorders against hypocretin-containing brain cells are probably triggered by environmental factors in genetically predisposed individuals.
- Traumatic brain injuries, tumors, or other diseases affect the parts of the brain that regulate wakefulness and REM sleep.
The causes of the type of narcolepsy not accompanied by cataplexy in which decreased hypocretin levels have not been observed are currently unknown.
In addition, age has been described as a non-genetic risk factor associated with the development of narcolepsy. Generally, narcolepsy begins in people between 10 and 30 years of age.
Symptoms
The development and severity of symptoms will vary greatly. Initially, they will appear one at a time and may be separated by long periods. Generally, the initial symptoms are mild but worsen with age and may progress at a variable rate. However, although they will never disappear, they may partially improve with time. Additional symptoms of narcolepsy include:
- Excessive daytime sleepiness (EDS): Everyone has this symptom, which is often the most obvious. It is characterized by persistent sleepiness in the form of a sudden sensation.
- Cataplexy is a sudden loss of muscle tone while a person is awake, leading to weakness and a loss of voluntary muscle control but maintaining full consciousness. It is often triggered by sudden, strong emotions. It usually appears weeks or years after excessive daytime sleepiness, with attacks of varying frequency, lasting only a few minutes and resolving on their own almost instantaneously.
- Sleep paralysis: temporary inability to move or speak while falling asleep or waking up that lasts seconds or minutes, and the person remains fully conscious. At the end of the episodes, the person recovers completely.
- Hallucinations may accompany sleep paralysis, usually when the person is falling asleep or waking up. Often, the content is visual, but other senses may be involved.
Additional symptoms that may accompany narcolepsy consist of:
- Insomnia, vivid dreams, apnea, externalization of dreams, and periodic leg movements may interrupt sleep during the night.
- Episodes of temporary sleep can last in the order of seconds during an activity, after which they continue without being able to remember what happened or be aware of what they are doing. It frequently occurs during routine activities such as talking, eating, writing, or driving.
Although daytime sleepiness occurs in all cases, only 10 to 25% will experience all the other associated symptoms.
Prevention
There are no effective measures for the prevention of narcolepsy. However, the following lifestyle changes focused on sleep hygiene may be helpful:
- Taking short, regularly scheduled naps when they tend to feel sleepier.
- Maintain a regular sleep schedule, even on weekends, to try to sleep better.
- Avoid caffeine or alcohol several hours before bedtime.
- Avoid smoking, especially at night.
- Exercise daily for at least 20 minutes, up to 4 or 5 hours before bedtime. This would favor a healthy lifestyle and avoid being overweight.
- Avoid abundant and heavy meals before going to bed since it makes it difficult to fall asleep.
- Relaxing activities before bedtime can help promote sleep (warm bath). Adjust the sleeping space to the right temperature and conditions.
Safety precautions, particularly when driving, are essential for people with narcolepsy. Excessive daytime sleepiness and cataplexy can lead to severe injury or death if left unchecked in ordinary, safe actions, such as descending a staircase.
