What is Narcolepsy?

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By Dr Simon Kyle

Narcolepsy is a nervous system disorder with a typical onset between the ages of 15 – 25 years which affects around 0.02% – 0.18% of the population. Although the condition is relatively rare, the daytime consequences of narcolepsy can be severely debilitating.

Symptoms of narcolepsy
Narcolepsy is a disorder most strongly characterized by periods of excessive and extreme sleepiness during the day. During these periods, a powerful urge to sleep develops, often resulting in a short nap or 'sleep attack'. These sleep attacks generally last for around 15 minutes, but may last longer, and result in the sufferer feeling refreshed and able to continue their day as normal. Patients with narcolepsy also tend to fall asleep much faster than healthy individuals and may experience the condition alongside other forms of sleep disturbance, for example, sleep paralysis and sleep fragmentation.

Narcolepsy may also present with 'cataplexy', a sudden loss of muscle tone, which prevents movement of body parts. Attacks of cataplexy are most often triggered by strong emotions such as laughter or anger and usually last for 30 seconds or less, meaning that they may be missed all together. During these attacks, jaw muscles become slack, the head will suddenly fall forward and the knees will buckle. In the most severe cases cataplexy may last much longer, leaving the person paralyzed for several minutes.

Normal sleep patterns will see people going through 2 main stages as they fall asleep, 'non-rapid eye movement' (NREM) first, and then 'rapid eye movement' (REM) sleep after a couple of hours. However, people with narcolepsy do not experience NREM sleep initially, and instead enter REM sleep, immediately. This can result in vivid dreams very shortly after falling asleep. REM sleep is the phase of sleep characterized by muscle atonia and intense dream content.

Scheduled daytime naps (called the multiple sleep latency test) at a sleep laboratory can help with the diagnosis of narcolepsy, where there are REM-sleep onsets in at least 2 out of 4 nap opportunities.

Causes of narcolepsy
Much remains to be discovered about the precise causes of narcolepsy, but some research suggests that it may be a genetic disorder, meaning that it is passed down through family members in their DNA. In particular, research has shown that people with narcolepsy, on average, tend to have lower levels of a protein called 'hypocretin' in their brains. The chemical hypocretin has an important role in regulating sleep patterns which has lead to the theory that narcolepsy could be an autoimmune disease, where the immune system attacks the body's own cells, in this case those responsible for producing 'hypocretin'.

It is likely though, that other, environmental factors, also contribute to the development of the disorder. Other known factors associated with the onset of narcolepsy include pregnancy, changes in sleep pattern, brain damage and severe stress. These are considered to be potential contributory factors as more than 50% of people with narcolepsy see events of this kind shortly before their symptoms develop.

Treatments for narcolepsy
At this point, there is no known 'cure' for narcolepsy but the sleep disorder may still be managed effectively and its symptoms controlled. Treatment includes a variety of lifestyle changes including eating lighter or vegetarian meals during the day and scheduling naps to control daytime sleep and reduce the number of unplanned, sudden sleep attacks.

Alongside these lifestyle changes, people may be prescribed stimulant drugs to boost energy during the day or antidepressants to help deal with symptoms of cataplexy and REM-related features such as sleep paralysis and hypnagogic hallucinations.

Filed under: Sleep disorders