Scientists have figured out why a small percentage of people require less than six hours of sleep, whereas the vast majority of humans need at least 8 hours a night to thrive.

Image via Huffington Post.

The researchers from the American Academy of Sleep Medicine conducted a study on 100 pairs of twins and identified a gene mutation that enables some of them not only to do well only sleeping 6 hours, but also to experience less effects after pulling an all-nighter. The gene in question is called BHLHE41 and the variant is called p.Tyr362His; interestingly enough, the results were even more significant than scientists expected – individuals with this variant slept on average 5 hours a night.

Cognitive tests were also conducted on the subjects and showed that following extended sleep deprivation, the twin without the variant slept for 9.5 hours while his brother or sister slept just eight hours to catch up.

“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,” says lead author Renata Pellegrino, PhD, senior research associate in the Center for Applied Genomics at The Children’s Hospital of Philadelphia. “The mutation was associated with resistance to the neurobehavioral effects of sleep deprivation.”

For the purpose of the study, all twins were the same sex, and 59 pairs were identical while 41 were dizygotic (from different zygotes) to limit external influences; the results were similar, regardless of the type of twins. Study participants were healthy.

Scientists warn that for people without the gene variation (most of the population), 5-6 hours of sleep is simply not enough – and that’s a biological need, not a personal preference.

“This study emphasizes that our need for sleep is a biological requirement, not a personal preference,” says American Academy of Sleep Medicine President Dr. Timothy Morgenthaler. “Most adults appear to need at least seven hours of quality sleep each night for optimal health, productivity and daytime alertness.”

Scientific Reference: Renata Pellegrino et al. A Novel BHLHE41 Variant is Associated with Short Sleep and Resistance to Sleep Deprivation in Humans. Sleep,