Important points
- A new study in Japan has found that just 20 minutes of exposure to natural light before you wake up can significantly reduce morning grogginess.
- This light cue helps regulate your circadian rhythm and boosts your energy, mood, and overall health. Its benefits are supported by leading sleep and heart health organizations.
- Natural light is best, but a sunrise alarm clock can effectively replicate its benefits, especially during dark months or when morning sunlight is limited.
For some people, wake up in the morning It’s easy. You can start each day feeling refreshed without even needing an alarm clock. And then there are the rest of us. Pressing “snooze” too many times And no matter what time I go to bed, my head feels groggy. Fortunately for us, new research Having left Japan, we have discovered that soaking up natural light in the morning can be helpful. Although this relationship has previously been studied in a medical context, this study takes an architectural approach to determine how this knowledge can be applied outside the laboratory. Here’s what the research found and how you can use natural light in your home.
How to use natural light to reduce morning fatigue
Research published in journals buildings and environmenttested three different morning scenarios: exposure to natural light from dawn until you wake up, exposure to natural light 20 minutes before you wake up, and no exposure to natural light before you wake up. The researchers found that the group who didn’t have exposure to natural light before waking up felt the most tired in the morning. Of the other two groups, those exposed to natural light for 20 minutes felt the least tired after waking up.
So why is more exposure bad when it comes to natural light in the morning? Dr. Daisuke Matsushita, lead author of the study, says this is due to the fact that the dawn time for natural light varies by season and region. The weather and window orientation also affect the amount of time a room is filled with natural light. “The sunrise time in Japan is from around 5 a.m. in the summer to 7 a.m. in the winter,” Matsushita explains. “In modern life, commuting times are fixed regardless of the time of sunrise. Morning light makes it easier to sleep, but 5 a.m. is too early. It feels like 20 minutes ago.” wake up is preferable. ”This is partly due to the light meanwhile Sleep is known to cause poor sleep, he explains.
Why does natural light help us wake up?
So why, exactly, does natural light have such a big impact on how we sleep and wake up? It’s because of our circadian rhythm, the internal clock that tells our organs what time it is outside, says sleep medicine physician Dr. David Benavidez.
“If you get the exposure timing wrong, [circadian] “Natural light provides the strongest and most robust signal to the circadian clock, allowing for optimal rhythms of hormones, mood, and behavior,” said neuroscientist Maj. Alison Brager.
many of us circadian rhythm Benavidez says it is genetically pre-programmed and we can influence aspects of it, and light is its most powerful external stimulus. “When light enters our eyes, it helps regulate the body’s master clock, also known as the suprachiasmatic nucleus, located in the brain,” he explains. “It tells us whether to speed up or slow down our time and rhythms. By mastering this concept, you can improve your sleep and wake timing, mood, energy, and overall health.”
But why is getting your circadian rhythm in order so important? “Circadian health is based on extensive research and clinical guidance, and sleep physician training is for good reason,” Benavidez says. “Optimizing circadian rhythm health benefits healthy people as well as those with sleep problems.” For example, in April 2025, the American Heart Association released the following report: scientific statement Healthy sleep includes not only sleep duration, but also timing, regularity, and circadian rhythms, highlighting that disrupted sleep independently increases the risk of hypertension, diabetes, obesity, and heart disease.
What about artificial light?
Research shows that to reduce morning fatigue, it’s ideal to spend 20 minutes exposed to natural light before you wake up. But letting in the perfect amount of natural light is easier said than done, unless you set your curtains on a timer or live with someone who opens them at a certain time each day.
This is where the sunrise alarm clock comes into play. Instead of waking you up with a harsh sound, this alarm clock gradually fills your room with light, mimicking dawn and brightening just before you wake up. Most are programmable and can be set to give you 20 minutes of light before you actually need to get out of bed. But is a sunrise alarm clock as effective as natural light?
According to Matsushita, natural light is preferable, although it has similar effects. “We have long adapted to periodic changes in natural light,” he explains. “Even if you simply match illuminance and color temperature, there are differences in spectral distribution and frequency, at least between natural and artificial light, and these differences can affect sleep quality.”
While Brager and Benavides agree that natural light is a better option, they believe sunrise alarm clocks can be an effective alternative, especially during the dark winter months. However, it is recommended to expose yourself to natural light as early as possible in the morning. “I typically recommend that patients go outside within 30 to 60 minutes if possible, or get up for at least 15 minutes and get some natural light,” Benavidez says.
