What is narcolepsy?
Narcolepsy is a neurological disorder characterized by extreme daytime sleepiness and uncontrollable episodes of falling asleep during the day. This excessive daytime sleepiness should not be mistaken for the afternoon slump, since neurological defects are responsible for narcolepsy, rather than just sleep deprivation or lack of caffeine!
Who is at risk of narcolepsy?
Family members of an affected individual have a 20X – 40X increased risk of developing narcolepsy, indicating a strong genetic basis for the disorder. The genetic variant most closely associated with narcolepsy is HLA-DQB1*06:02. Individuals with this variant have a 7X to 25X increased risk of developing narcolepsy, although one recent European study indicates a much higher odds ratio of approximately 250-fold! Multiple other HLA-DQB1 variants also exist, and many of these provide some protection from narcolepsy, complicating the risk analyses.
What are the symptoms of narcolepsy?
Narcolepsy is often incorrectly diagnosed because it involves a wide variety of neurological symptoms. The symptoms include:
- Excessive daytime sleepiness (100% of affected individuals)
- Cataplexy – a sudden loss of voluntary muscle tone (70% of affected individuals)
- Sleep paralysis and/or vivid hallucinations (10 to 20% of affected individuals)
- Microsleep (sleep episodes that only last a few seconds)
- Nighttime wakefulness
- Atonia (loss of muscle strength)
- Involuntary leg muscle contractions
- Rapid entry into REM sleep
How common is narcolepsy?
Between 1 in 2000 and 1 in 5000 people are thought to be affected by narcolepsy. However, only about 25% are correctly diagnosed, and often people are instead mistakenly diagnosed with psychiatric or emotional problems. Family members of an affected individual also have a 20X – 40X increased risk of developing narcolepsy, indicating a strong genetic basis for the disorder.