A genetic variant has been linked to a higher risk of the sleep disorder narcolepsy by Japanese scientists.

Published in the journal Nature Genetics and carried out by staff from the University of Tokyo, the study examined the genetic code of several hundred volunteers, some of who had narcolepsy and others who did not.

The variant they found was linked to a 79 per cent higher risk of narcolepsy in Japanese people, with a 40 per cent increased chance in other ethnic groups.

"It is found close to two genes, CPT1B and CHKB, which have already been singled out as candidates for involvement in the disorder - as they both have a role in regulating sleep," the BBC reports.

The researcher said they think the results of their study could help physicians to understand the underlying mechanisms responsible for the sleep disorder, especially what causes the shortage in the neuropeptide hormone hypocretin, which many scientists believe is the cause of narcolepsy.

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