Why some people can cope with short sleep

Most people require seven to nine hours of sleep to have proper daytime functioning, but some people can function normally on less than six hours of sleep per night owing to a gene mutation, says a study.

The genetic variant also appears to provide greater resistance to the effects of sleep deprivation, the researchers, who studied 100 twin pairs, noted.

People with p.Tyr362His - a variant of the BHLHE41 gene - had an average nightly sleep duration of only five hours, which was more than one hour shorter than the non-carrier twin, who slept for about six hours and five minutes per night.

The twin with the gene mutation also had 40 percent fewer average lapses of performance during 38 hours without sleep and required less recovery sleep afterward - sleeping only eight hours after the period of extended sleep deprivation compared with his twin brother, who slept for 9.5 hours.

"This work provides an important second gene variant associated with sleep deprivation and for the first time shows the role of BHLHE41 in resistance to sleep deprivation in humans," said Renata Pellegrino, senior research associate at The Children's Hospital of Philadelphia in the US.

The study group comprised 100 twin pairs - 59 monozygotic pairs and 41 dizygotic pairs - who were recruited at the University of Pennsylvania.

Response to 38 hours of sleep deprivation and length of recovery sleep were assessed in a sleep lab. During sleep deprivation, cognitive performance was measured every two hours using the Psychomotor Vigilance Test.

The study appeared in the journal Sleep.