You know those people -- yeah, those people -- who never seem to need more than a few hours' sleep a night, and can function like a perfectly alert human being the next day?
A new study in the journal Molecular Psychiatry shows that their ability to do so might lie in their genes.
Scientists from around the world, led by researchers from Ludwig-Maximilians-Universitaet Muenchen, conducted a genome-wide association study to find that a variation of the gene known as ABCC9, which is already known to play a role in heart disease and diabetes, can also affect how long we sleep.
The researchers looked at the genes of 4,000 people from around Europe and found that people who had two copies of the ABCC9 gene were able to sleep for much shorter periods of time than people with two copies of another version of the gene.
Researchers further confirmed the finding in fruit flies.
"So apparently the relationships of sleep duration with metabolic syndrome symptoms can be in part explained by an underlying common molecular mechanism," study researcher Dr. Karla V. Allebrandt, a chronogeneticist at LMU Munich, said in a statement.
ABC News reports that past research has also demonstrated that genetics might explain why some people feel really tired even though they've gotten a full night's sleep.
"Our society has equated sleepiness with defects of character, like laziness and depression, but really, some people are generally sleepier during the day," Dr. Mark Mahowald, medical director of the Minnesota Regional Sleep Disorders Center, told ABC News. "We have to accept the fact that sleep duration is genetically determined and not a sign of a defect."
Generally, the National Sleep Foundation reports that most healthy adults need about seven and eight hours of sleep a night, though that number can change depending on our "sleep debt" -- lost sleep as a result of being woken up, not getting enough sleep, and other factors.
CORRECTION: A previous version of this article mistakenly stated that the study was published in the journal Nature. It has been corrected to show that the study is published in one of Nature Publishing Group's review journals, Molecular Psychiatry.