Narcolepsy

Chronic neurological disorder characterized by the inability to regulate sleep-wake cycles. It can interfere with psychological and social development, and interfere with academic and work activities. It has an annual incidence of 50 cases per 100,000 individuals and although there is no cure, treatment and lifestyle changes allow control of the disease.

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 cases of narcolepsy accompanied by cataplexy. Some of these currently suggested causes include the following:

  • Autoimmune disorders against hypocretin-containing brain cells probably triggered by environmental factors in genetically predisposed individuals.
  • Traumatic brain injuries, tumors or other diseases affecting 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.

Narcolepsy is associated with both genetic factors and environmental triggers. Family studies have shown a risk up to 40 times higher in first-degree relatives, and twin studies have shown a heritability close to 35%. Recently the UK Biobank project has evaluated over 50,000 participants for genetic factors associated with this condition, and as a result 23 susceptibility loci significantly related to the development of this sleep disorder have been identified.

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): all people have this symptom which is often the most obvious. It is characterized by persistent sleepiness in the form of a sudden sensation.
  • Cataplexy: 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 that may interrupt sleep during the night.
  • Episodes of temporary sleep that can last in the order of seconds during an activity and after which they continue with the activity without being able to remember what happened or awareness of what they are doing. It frequently occurs during routine activities such as talking, eating, writing or driving.

Although in all cases there is daytime sleepiness, 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 and beneficial:

  • 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 a day, up to 4 or 5 hours before bedtime. In addition, it would favor a healthy lifestyle to 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 important for people with narcolepsy. Excessive daytime sleepiness and cataplexy can lead to serious injury or death if left unchecked in ordinary safe actions, such as descending a staircase.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

20 loci

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