Why Some People Are Wired to Wake Up Early, According to Experts

If you've ever wondered why some people can wake up before sunrise without an alarm while others struggle to get out of bed on time each morning, the answer lies in biology. Our circadian rhythm, also known as our internal body clock, largely influences our natural sleep-wake preferences, known as chronotypes.

That doesn't mean your daily habits don't matter. Light exposure, regular exercise, and consistent sleep schedules can also influence when you feel tired and when you wake up, our experts reveal. But for some people, rising early comes more naturally than it does for others. To better understand why some people are early risers—and whether night owls can shift their schedules—we asked sleep experts to explain the science behind it.

Why Some People Naturally Wake Up Earlier

The chronotype largely determines whether someone is a morning person. Your chronotype is driven by the circadian rhythm, the body's internal clock that regulates sleep, alertness, and other daily functions, explains Jennifer Martin, a professor at Florida International University's College of Medicine. Genetics largely determines our circadian rhythm, and having an early or late chronotype often runs in families.

People whose internal clocks run slightly shorter than 24 hours tend to feel sleepy earlier and wake up earlier, making them more likely to be morning people, says Kenneth Wright, a professor and director of the Sleep and Chronobiology Laboratory in the Department of Integrative Physiology at the University of Colorado Boulder. Those whose internal clocks run slightly longer than 24 hours are more likely to stay up later and wake later, giving them "night owl" tendencies.

For early types, melatonin—the hormone that promotes sleep—begins rising earlier in the evening and declines earlier in the morning. As a result, they naturally feel sleepy sooner and wake up earlier.

As melatonin levels fall in the morning, cortisol levels begin to rise. "One of the major events that happens is a rise in cortisol concentrations that anticipates wake time," says Jamie Zietzer, a professor in the Department of Psychiatry and Behavioral Sciences at Stanford University. "This rise in cortisol helps free up energy that is important for increasing your cardiovascular tone."

How Your Daily Habits Affect Your Sleep Schedule

Biology provides the foundation of the chronotype, but habits and environmental factors can significantly influence sleep schedules and daytime alertness, Martin says. "Most people are not 'definite' morning or evening types; they fall into the moderate morning or evening types or neither," Zieter says. "In these individuals, there is a certain degree of flexibility in terms of how much their chronotype can be influenced by habits and environment."

Having exposure to natural light in the morning helps reinforce the body's internal clock and encourages earlier sleep and wake times, Wright says. In addition, consistent sleep schedules, regular physical activity, and limiting bright light exposure in the evening can also support an ideal sleep schedule for early rising.

Other factors can also shift sleep schedules later, including drinking caffeine late in the day, spending less time outdoors, and exposure to artificial light—especially from screens and indoor lighting after sunset, Wright says.

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While our habits and environment play a role in our sleep schedules, they may not completely change whether someone is naturally an early or late type, especially if you are an extreme type. But tweaking habits and environmental factors to reinforce an early type can help optimize sleep and improve how alert you feel throughout the day, Martin says. People with extreme late types usually have a harder time making lasting changes, and their natural tendencies often return if they stop following a strict routine, Zeitzer adds.

For late types, the goal isn't necessarily to become a "morning person," but rather to adopt a schedule that allows a sufficient amount of sleep in order to feel more alert in the morning, and meet work, school, or family obligations.

Wright says the most effective way for a late type to shift to an early type is by getting light exposure first thing in the morning. This could be through routine morning walks outside, sitting near sunny windows, and spending more time outdoors, he adds.

In the evening, decrease light exposure by dimming lights at home and reducing time in front of screens to shift the body's internal clock earlier. Keeping your bedroom as dark as possible while sleeping can also support the adjustment by reinforcing the body's natural sleep signals and helping maintain a consistent sleep-wake cycle, Wright says.