Japanese researchers have discovered a genetic variant that could one day help to explain the mechanism underlying narcolepsy. People with narcolepsy experience sudden muscle weakness and extreme daytime sleepiness that can result in them falling to sleep at any point of the day, sometimes several times a day. Many people with narcolepsy also experience "cataplexy", in which muscular weakness or collapse follows an emotional event like surprise or laughter.
Although narcolepsy affects roughly one in every 2,500 people, the incidence in Japan and Korea is roughly four times higher. Professor Katsushi Tokunaga, of the department of human genetics, University of Tokyo, says he is unable to explain why both Japanese and Koreans appear more prone to narcolepsy. Professor Tokunaga hopes that his findings might help unlock the mystery and might also contribute towards novel treatment approaches.
During the study, genes from 222 people with narcolepsy were studied, and compared with the genetic profiles of people without the disorder. Two genes, CPT1B and CHKB, are already strongly suspected as having a role in the disorder as they are known to be involved in sleep. The new variant is close to these genes and is associated with nearly an 80 percent higher chance of narcolepsy in Japanese people, but only a 40 percent chance in other ethnic groups.
Scientists are also examining the genes as to their role in the production of the chemical hypocretin, thought to send signals to the brain about when to sleep and wake. One possibility is that people with narcolepsy experience a shortage of hypocretin and the gene variant might help to explain the mechanism affecting this shortage.
Dr Renata Rihan, a UK sleep specialist, commented on the findings to the BBC health news site. "The findings are interesting but preliminary - the exact function of the genes has been largely determined in mice, which may not necessarily translate to human biology." Dr Rian went on to say that the findings, ". . . in no way explains why others develop the disease and why some of those carrying the abnormal allele (variant) don't."
The study is published in the journal Nature Genetics.
Published On: October 10, 2008