A newly published study finds a tiny genetic mutation in people who genuinely need less sleep.

Why do some people only need four or five hours of sleep to be focused, functioning humans during the day? While sleep needs generally vary from person to person, certain individuals seem to thrive on alarmingly little sleep—without the detrimental effects of sleep deprivation others might experience on such few Zs. It turns out, it’s not purely to make the rest of us—who need a solid seven to nine hours of nightly shut-eye to stay healthy—feel inadequate.

According to a scientific paper recently published in Science Translational Medicine, their need for less sleep is due (at least in part) to their genetic makeup. Researchers at the University of California, San Francisco, have pinpointed a particular gene alteration, or mutation, occurring in short sleepers’ DNA that helps explain why and how short-sleepers can snooze for such brief durations without mood, memory, or physical impairment.

The study’s authors analyzed certain subsets of DNA present in a family of short sleepers—a father and son who only need around six and four hours a night, respectively. In both father and son, researchers found a “point mutation” in the gene responsible for the short sleep phenotype (called neuropeptide S receptor 1), which codes for a neuron receptor responsible for keeping people awake. According to Wired.com, one of the study’s authors, Ying-Hui Fu, PhD, believes this rare mutation could promote more efficient sleep in those who carry it, which could help us understand why short sleepers need less sleep.

It turns out that even mice bred for this particular gene mutation sleep for less time without exhibiting typical signs of sleep deprivation. One of the biggest side effects of serious sleep deprivation is a deficit in memory storing, processing, and retrieval. However, mice carrying the short-sleep gene mutation not only slept less (an amount that might otherwise cause the average individual to be sleep deprived), but were not susceptible to memory deficits associated with sleep deprivation.

So what does this mean for you? Mainly, it helps demonstrate that we shouldn’t be comparing our sleep habits to other people’s. Everybody’s body clock, or circadian rhythm is slightly different: A morning person should never judge a night owl for staying up late and sleeping in late. And if you’re someone who requires a full nine (or even 10) hours of sleep, there’s a reason for that; don’t try to force yourself to sleep on five hours. Leave that to the rare, genetically blessed, short sleepers in your life.