If you’ve ever wondered why some people can get by on just a few hours of sleep while others need much more, scientists may have found an answer.

Research conducted on 4,000 Europeans discovered that those who had two copies of a particular variant of a gene called ABCC9, which influences sleep duration, generally reported sleeping less than those who had two copies of a different version of the gene.

“Our society has equated sleepiness with defects of character, like laziness and depression, but really, some people are generally sleepier during the day,” said Dr. Mark Mahowald, medical director of the Minnesota Regional Sleep Disorders Center. “We have to accept the fact that sleep duration is genetically determined and not a sign of a defect.”

In previous studies, the ABCC9 gene was linked to heart disease and diabetes, so the most recent research could also suggest a connection between sleep and cardiovascular health.

[ABC News]