More Daylight Improves Sleep and Mental Health, Research Finds

Do you start your day by rolling out of bed and pulling back the curtains to let in the morning sunlight? If not, research shows you might be doing your circadian rhythm a disservice.

A new study that builds off of previous research on the effect of daylight exposure on circadian rhythm shows that soaking up more sunlight at home can improve circadian alignment, sleep quality, and mental health.

The Study

In this recent field study, a group of researchers from the Light and Health Research Center at Mount Sinai's Icahn School of Medicine observed participants in their homes, living their everyday lives, and adjusted daylight exposure to determine its effects on circadian rhythm, sleep and mood.

Circadian rhythm refers to the physical, mental and behavioral changes the body experiences over a roughly 24-hour period. These rhythms are regulated by our biological clock, respond largely to light-dark patterns and have a major impact on our health—perhaps most noticeably, our sleep patterns.

One interesting aspect of this study is the design of participants’ natural habitats. While most buildings are designed to let daylight inside, we often use blinds and curtains to minimize the heat and glare that accompany that light. In this study, electrochromic glass was used, a technology that applies a low-voltage electric current between the window’s layers of glass, effectively tinting the window. This type of glass automatically responds to the presence and timing of solar radiation while still allowing for short-wavelength light, which affects the circadian system.

Thanks to this technology, the study environment was more easily controlled, as electrochromic glass allows for more daylight by minimizing glare and heat. To determine the effect of increased daylight, the 20 participants spent one week in their apartments with the electrochromic windows, and one week with functionally standard windows with blinds.

The findings, published in the International Journal of Environmental Research and Public Health, revealed that participants experienced stronger circadian alignment, earlier and more regular sleep and improved vitality and mental health when exposed to more daylight.

“The fact that humans spend nearly 90% of their time indoors, it is critical to incorporate daylighting solutions in buildings that go beyond meeting visual task requirements and promote circadian alignment and health more broadly,” the study says.

While the sample size of this particular study may be small, the research presents unique insight by reporting from within real-world conditions while building on previous literature on light, sleep and circadian rhythm.

“All of the outcome measures were consistent with what we hypothesized based on the more controlled laboratory studies we performed and based on what we know about the impact of light on circadian rhythms,” says study author Mariana Figueiro, PhD.

These findings are interesting and nicely documented, says David Rapoport, MD, research director at Mount Sinai Health System’s Integrative Sleep Center and advisor to sleep fitness company Eight Sleep. But they’re not surprising.

“This is one of many studies showing that we are influenced by our environment of light in very specific ways,” says Dr. Rapoport. “It supports the idea that getting light that is in sync with what our biology was designed to do is actually associated with lots of benefits.”

Setting Your Inner Clock

Poor quality of sleep has been associated with several negative health effects, including brain fog, immune system disruption and increased risk of depression, diabetes, heart disease and high blood pressure.

Fortunately for the average person, there are easy adjustments that can be made in daily life to better align your internal clock and improve sleep. However, it should be noted that some people live with chronically deviant circadian rhythms and these recommendations might not be helpful for this population, who should seek professional help.

Rapoport notes that, to reap the benefits of a regular sleep schedule, the first step is to be conscious that this matters. Paying attention to the amount of light you’re exposed to each day, as well as keeping a consistent schedule are key parts of the equation.

“If you can think of light as one of the essentials of good health, regularity of sleep is one of the [factors] we can also address by your behavior,” he says. “Going to bed at the same time every night and getting up at the same time is a very important part of setting that clock and getting that benefit. Light helps you do it, but you can do it just by your behavior.”

Avoiding the temptation to work late into the night or to sleep in on the weekends can help regulate your sleep schedule. Taking measures to ensure daylight exposure are important, as well.

“The simplest solution is to open your blinds during the day,” Rapoport says. “Don’t be lazy, don’t leave your blinds down all the time.”

Go outside during significant points of the day, especially in the morning. Rapoport suggests taking a walk after waking up, and Figueiro recommends spending time in the backyard or on the porch to greet the day.

Situate your desk or workspace so that you’re facing a window. And if your office, or wherever you’re spending most of your day, is in your basement, add a couple extra light fixtures to keep on during daylight hours.

At night, dim the lights and avoid blue light, especially, which is most commonly emitted from screens. There are settings on most computers, phones and tablets to reduce blue light exposure at nighttime. In some cases, you can set a timer to change your display settings automatically.