Most people wouldn’t dream of functioning on only a few hours’ sleep per night if they had the choice. After all, sleep deprivation is nothing to snore at: People who routinely get fewer than eight hours of sleep a night often experience impaired memory, depression, decreased immunity and increased sensitivity to pain.

But a new study shows that some people are genetically inclined to need less sleep… and they do just fine without it.

Scientists have been trying for decades to understand what regulates our mysterious need for sleep. Several genes are thought to play a role in the body’s daily cycle of activity… officially known as the circadian rhythm… but much remains a mystery. So when researchers at the University of California stumbled across a mother-daughter pair who claimed they only needed six hours of sleep a night, the “short sleepers,” as they were nicknamed, became the focus of a study to determine how sleep cycles are regulated.

Experts say only five percent of the human population are true “short sleepers,” and that these people remain in perfect health despite getting much less sleep than is required by the average person. The mother-daughter pair both had mutations in a gene that controls the circadian rhythm. Researchers speculated that this mutation allowed the short sleepers to sleep more deeply and enjoy more intense stages of rapid eye movement, the sleep cycle when dreams occur.

But when it comes to the rest of us, we still need plenty of shuteye to operate at our best… at least seven to eight hours of it.