Genetic clue uncovered for narcolepsy
Last Updated: Monday, September 29, 2008 | 12:16 PM ET
CBC News
A genetic variant may predispose people to narcolepsy, Japanese researchers have found.
Narcolepsy causes extreme daytime sleepiness, and may lead people to doze off while driving, as well as sudden, temporary muscle weakness called cataplexy triggered by strong emotions such as anger or laughter.
Since the condition appears to run in families, researchers at the University of Tokyo compared the genetic code of 159 people with narcolepsy, to 389 controls who did not have the disease to look for genetic links.
Narcolepsy occurs in about 1 in 2,500 individuals in the United States and Europe, about the same as Parkinson's disease, but is at least four times more frequent among Japanese, the researchers said.
A genetic variant called rs5770917 was linked to 1.79 times the odds of narcolepsy among Japanese people with the disorder, Katsushi Tokunago and colleagues reported in Sunday's online issue of the journal Nature Genetics.
The variant was also common among Koreans, but not among individuals of European or African descent, the researchers said.
The variant is found near two genes, CPT1B, and CHKB, that are implicated in regulating sleep and are thought be involved in narcolepsy.
The cause of narcolepsy is unclear, but a chemical called hypocretin is absent in the brain of people with the condition. Hypocretin sends wake up signals to the brain.
Currently, the daytime sleepiness that occurs with narcolepsy is often treated with stimulants. The genetic findings could help researchers to understand the cause of the shortage of hypocretin.
"We hope that the discovery of the present susceptibility gene[s] might contribute to the establishment of novel therapeutic approaches," the study's authors wrote.
Researchers do not know why some people who have the variant do not develop the narcolepsy.
