Researchers from the University of Tokyo have identified a genetic variant linked to a much higher risk of narcolepsy, which may explain the cause of the condition.
Narcolepsy is a rare condition which causes extreme daytime sleepiness, impaired vision and sudden muscle weakness. Sufferers suddenly fall asleep without any warning during a normal activity, and some of them also suffer from "cataplexy", where strong emotions such as anger, surprise, or laughter can trigger loss of muscle strength or lead to collapse.
Scientists believe the cause of narcolepsy may be related to a shortage of a chemical called hypocretin which sends signals to the brain about sleeping and waking up. The condition occurs in 1 in every 2,500 people in the United States and Europe, but is at least four times more common in Japan.
The Japanese researchers analyzed the genomes, or DNA, of 222 narcoleptic Japanese and 389 others who did not have that condition, as well as 424 Koreans, 785 people of European descent and 184 African Americans.
The research found one gene variant occurred with significant frequency among those with narcolepsy and it was linked to an 79% higher chance of narcolepsy in Japanese people, and a 40% increased chance in other ethnic groups - it occurred with significant frequency among narcoleptic Koreans, but the association was not evident in the Europeans and African Americans.
The culprit gene is found close to two genes, CPT1B, and CHKB, which have already been identified as candidates for involvement in the disorder as they both have a role in regulating sleep.
This research could be vital because treatments usually focus on dealing with the symptoms of narcolepsy, but knowing the genetic cause may help to understand underlying cause - in particular what was causing the shortage of hypocretin.
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