Tokunaga and colleagues at the University of Tokyo believe they have identified a mutated gene that is linked to narcolepsy.  This study showed that the genetic variant known as rs57770917 is suspect.

Narcoleptic tetrad consists of the following symptoms:  excessive daytime sleepiness, hypnologic hallucinations, cataplexy, and sleep paralysis.  Hypnologic hallucinations are vivid dreams at the onset of sleep.  Cataplexy is the sudden loss of muscle tone, normally triggered by an emotional response.

In the United States, the prevalence of narcolepsy is approximately on in every 2,500 people.  This varies across countries, with Japan having four times the prevalance as the U.S.

Genetic transmission in canines has been successful since the 1970s.  Stanford University has maintained a colony of narcoleptic Doberman Pinschers for some time now.  In humans, there is approximately a 1% to 2% increase of prevalence for first degree relatives (Mignot 1998).

Twin studies suggest that more than just genetics play a role in narcolepsy.  Environmental factors can increase the risk.  Head trauma, various infections and changes in the sleep-wake cycle can be influencing environmental factors.  The onset of narcolepsy is also normally during adolescence, not at birth, which also supports the idea that narcolepsy is affected by environmental factors.  This concept is also supported by the University of Tokyo study … ten percent of the Japanese population contain this mutated gene, but only about 0.2 percent suffer from narcolepsy.  Tokunga and colleagues explain this by noting there may be additional genes that play a role.

Predisposing factors are not always predictive of a condition.  Behavior or environment always has an impact on the condition.  Narcolepsy may be one condition in which genetic factors play a larger role than behavior and environment, but to exclude them is also a mistake.  The nature vs. nuture debate continues.

Luke Goodpaster

Director of Research

The Sleep Wellness Institute

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