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Some people naturally wake up effortlessly between 4 and 5 AM, well before dawn. They feel energized and are ready to take on the world with a smile on their face. The “snooze” function on their phones is superfluous.

Although the author of this article clearly doesn’t fit the profile, quite a few do. According to a new study, one in every 300 people might have the genetic markers of “advanced sleep phase” (ASP), which makes them very early risers — that’s a lot more than previously estimated. What’s more, one in every 475 people seems to have familial advanced sleep phase (FASP), which means that ASP genes run in the family.

The study was led by Dr. Louis Ptacek, who is an expert in circadian rhythm genetics at the University of California San Francisco. The circadian rhythm, also sometimes referred to as the circadian clock, is a biochemical mechanism that allows living organisms to sync their sleep-wake cycle to the 24-hour cycle of a day. Essentially, it’s our daily rhythm. One of the key factors influencing the workings of this rhythm, perhaps unsurprisingly, are levels of ambient light, but things like temperature can also play an important role.

It’s long been known that the older you get, the less you sleep. There a few reasons why this may happen, including medications, psychological distress, retirement, or simply the theory that the elderly need less sleep. But for the purpose of their study, Ptacek and colleagues only included people who rise between 3 and 5 A.M. and are under the age of 30.

The researchers evaluated 2,422 people who sought treatment at a sleep clinic. In order to find the individuals who best fit the FASP criteria, each participant also had to answer two important questions: 1) On a long weekend or vacation with few or no responsibilities or obligations when would you go to bed? and 2) On a long weekend or vacation with few or no responsibilities or obligations, when is your final awakening for the night?

Most people look forward to the weekend for some much needed extra shut-eye, but the most extreme early birds tended to stick to their rigid sleep schedules. On weekends, these individuals only slept in for five to ten minutes whereas normal sleepers took an extra 30 to 38 minutes on average.

Out of the 2,422 people included in the study, 12 were extreme early birds who met ASP criteria, five of whom also met FASP requirements. All of them had at least one first-degree family member that had the same extreme morning schedule, the authors reported in the journal Sleep.

The authors claim that their findings “can guide clinicians on the utility of screening for extreme chronotypes both for clinical decision-making and to flag prospective participants in the study of the genetics and biology of FASP.”

Waking up really early sounds appealing. You can get a lot of work done, for instance, before anyone else wakes up and then have the rest of the day to yourself. But this also means that your life is offset from everybody else’s schedule. So early larks usually either sacrifice their social life or have to deal with sleep deprivation when they have to attend social events and late-night diners. It’s still better than the alternative — being a night owl.

Speaking of which, the researchers say that genetic factors are most evident in extreme behaviors and phenotypes (the expression of a gene, i.e. blue eyes, blond hair). If there’s a genetic component for waking up early, likewise there should be one for staying up late. Like night-shift workers, night owls are living out of sync with their natural rhythms and are thus at risk of various health problems from obesity to breast cancer.

Previously, a study that included 250,000 American participants, whose genomes were analyzed by private company 23andMe, and 450,000 British participants who were part of the UK Biobank study, identified several genes variants associated with being a morning lark or night owl. The authors also identified associations between waking up early and greater psychological well-being and a lower risk of mental disorders, such as schizophrenia and depression.