man looking at blue light on his phone while laying in bed
Sleep Health

Why Blue Light Might Be Keeping You Up at Night

Last Updated
March 15, 2021
min read


When I’m trying to live my best, healthiest life—and most of us are—I pay daily attention to how I’m treating my body. I watch the food I’m eating, the exercise I’m getting and set my alarm to make it to spin class a couple times a week. I also pay close attention to how much blue light I’m exposed to before bed.

What exactly is blue light? Blue light is a color in the visible light spectrum that can be seen by human eyes. Blue light is a short wavelength, which produces higher amounts of energy. We are primarily exposed to it through our cell phones, computer screens and televisions.

So how much thought should we give to light exposure? I tell all my patients: light is medicine. Just like you wouldn’t expect to feel healthy after eating junk food all day, you can’t consume all kinds of junk light all the time and expect to feel, sleep, and perform well. Managed well, light exposure can boost performance, improve sleep, and increase energy and in today’s lit-up world, being a savvy consumer of light can help you protect your health and sleep.

In the modern world, light is everywhere we turn, and we have to actively seek out darkness. There’s also more blue-wavelength light than ever. Why is blue light significant? Let’s find out.

How nighttime blue light interferes with sleep

I’ve seen an avalanche of evidence in recent years about the potential hazards of blue-wavelength light.

Scientific studies have pinpointed blue light as a form of light that’s especially aggressive in triggering sleeplessness. Blue light suppresses melatonin production for more than twice as long as other light wavelengths, and alters circadian rhythms by twice the degree. Interference with the body’s 24-hour circadian rhythms can have a significant effect on health, creating problems with the cardiovascular, metabolic, and immune systems, disturbing mood, and compromising cognitive function. When your circadian rhythms are out of whack, you think, feel, and perform below your best—and over time, your health can be put at risk.

New research adds to this already large body of evidence of the power of blue light to interfere with sleep. A study of healthy young adults found exposure to blue light from computer screens between the hours of 9-11 p.m.: shortened their total sleep time, significantly suppressed melatonin production and diminished sleep quality by increasing the frequency of nighttime awakenings.

Researchers also found blue light prevented body temperature from dropping during the night. A gradually lowering body temperature is one key element of the body’s progression into sleep. That blue light kept body temperature elevated to daytime levels is a sign of the degree to which nighttime blue light exposure can disrupt normal circadian rhythms. After nights of blue-light exposure, participants were more tired during the day, and experienced more negative moods.

The takeaway? Nighttime blue light exposure is indeed harmful to sleep and circadian rhythms. And taking steps to manage blue light exposure—including using red light sources during evening hours—can make a real difference.

When blue light is beneficial

While a hazard to health and sleep at night, blue light exposure can be helpful during the day—especially in the morning and early afternoon. Research shows exposure to blue-light during daytime hours can be beneficial in several ways, including:

  • Reducing daytime sleepiness
  • Speeding reaction times
  • Elevating alertness
  • Strengthening attention span

Research suggests we don’t need prolonged exposure to blue light to achieve its benefits. A study found 30 minutes of blue-light exposure in the morning led to better working memory performance and faster reaction times, compared to other light exposure. Part of managing light exposure in today’s world is understanding how light can be used to enhance performance and support good health and sleep.

Ways to regulate blue light exposure

  • Carotenoid supplements – Research suggests carotenoid supplements may help strengthen the eye’s natural ability to block blue light. The eye has its own blue-light shield— called the retinal pigment epithelium, a thin layer of cells near the retina. This epithelial layer protects the retina against macular degeneration and acts as a filter for blue-wavelength light.
  • Blue light filtering software and apps – There are a number of apps that work to reduce blue light exposure during evening hours. Many smartphones and tablets include these blue-light filtering apps as part of their operating systems.
  • Blue-light blocking filters and glasses – Both filters for screens and blue-light blocking eyewear are available, to reduce unwanted, poorly timed exposure.
  • Targeted, specialty light bulbs – One of the most effective ways to manage light exposure is to use LED light bulbs that provide the specific kind of light that’s best for day and night. Energy efficient LED light bulbs are now made with our circadian biology in mind, designed to minimize the negative effects of blue wavelength light at night—and take advantage of those stimulating effects during the day.

A few key things to remember:

  • Get plenty of light exposure throughout the day. Light exposure during the day boosts attention and alertness, improves mood and cognitive function, strengthens circadian rhythms and can help you sleep better at night. Spending 10 or 15 minutes in the sunlight during the day—first thing in the morning, or on a break at lunch—is a healthful, nourishing light routine.
  • Keep screens away from your face at night. It’s one thing to relax in front of the television for a while during the evening, and quite another to have your head buried in your smartphone right up until lights out. The degree and intensity of artificial and blue-wavelength light exposure matter. As part of your Power Down Hour™, give yourself a mobile device cut-off time. That’s when you’ll stow your phone for charging—somewhere other than your bedside table. The closer you get to bedtime, the less interactive your media consumption should be.
  • Modern light exposure requires modern solutions and strategies. Pay attention to your “light diet,” and use the help that’s available to make the light in your life work on behalf of your health and well-being.

About the authors

Dr. Michael Breus