How Blue Light Affects Our Health

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Whether by straining our eyes or disrupting our sleep schedules, our constant exposure to blue light is harming our health.
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The sun is the largest source of our exposure to blue light, and during the day this light is natural and beneficial.
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"Blue light" is the range of visible light on the electromagnetic spectrum from 380 to 500 nanometers.

If you’ve shopped for eyeglasses or browsed digital apps lately, you may have noticed products claiming to reduce your exposure to blue light. What’s up with blue light, and why would you want to cut back on it?

You probably don’t think about light as having much of a color, but if you’ve looked at the nighttime glow from digital devices, including smartphones, laptops, and flat-screen TVs, you may have noticed a blue tinge. That’s because they’re illuminated with light-emitting diodes (LEDs), which are especially rich in “blue light” — visible light with a wavelength on the electromagnetic spectrum that ranges from 380 to 500 nanometers. Common energy-efficient LED lightbulbs and compact fluorescent lamps also emit a lot of blue light, unlike older incandescent bulbs.

The biggest source of blue light is the sun. But sunlight isn’t available 24/7, whereas the artificial blue light from digital devices and lightbulbs is. That’s where the problem lies. Whether straining our vulnerable eyes or disrupting our natural sleep schedules, our constant exposure to blue light is harming our daily well-being. Disrupted sleep can lead to decreased brain function. And the underlying cause of this disrupted sleep, a decline in the body’s production of melatonin, may increase the likelihood of certain cancers. Luckily, we can do something about these risks.

Light and Eye Health

Most obviously, staring at digital screens for several hours a day may cause eye strain, which can result in blurry vision, dry eyes, and headaches. Beyond that, it’s unclear whether modern-day exposures to blue light from digital devices pose a special risk to our eyes.

“Although blue light isn’t nearly as harmful to the eyes as ultraviolet (UV) light, it still has some of the same properties, so some scientists are concerned it may contribute to eye damage over time,” says Geoffrey Goodfellow, OD, an associate professor at the Illinois College of Optometry in Chicago. There’s no direct proof of this damage in the general population, but some research suggests that people with low blood levels of certain antioxidants may be more vulnerable to macular degeneration related to blue light exposure.

Many optometrist offices sell glasses with special lenses to help filter out blue light from digital devices, and numerous non-prescription options are available online. However, Goodfellow cautions that we don’t want to screen out all blue light during the daytime, such as by wearing 100-percent blue-blocking glasses. Blue light during the day helps keep our internal clock in rhythm and may help boost alertness and mood, as well as support memory and brain function. Plus, filtering out all blue light can distort colors. Due to this, the optical company Essilor and the Paris Vision Institute developed glasses with a feature that blocks about 20 percent of blue light — primarily deflecting the rays at the lower end of the blue light spectrum most likely to harm our eyes while transmitting the beneficial ones.

Timing of Light

While some blue light during the day keeps our body clock on track, exposure to excessive light in the evening may interfere with sleep and potentially increase risk of certain cancers, obesity, heart disease, diabetes, and psychiatric disorders. This risk is attributed, at least in part, to the potential of light at night to disrupt our circadian rhythm, the 24-hour cycle of various biological processes in the body such as alertness, hunger, and rest.

“There’s a master clock in your brain that keeps track of time,” says Richard Hansler, Ph.D., a retired General Electric lighting expert who now researches the effects of light on health at John Carroll University in Ohio. “The master clock gets its information about light and dark from special sensors in the eye. In the evening, that clock signals the pineal gland in the brain to start making melatonin — a hormone that helps us sleep.”

If you get too much light in the hours before bed, it can suppress your body’s production of melatonin. “Although too much exposure to any light can do this, we’ve found that suppression of melatonin is greatest with exposure to blue light in the wavelengths of 460 to 480 nanometers,” says George Brainard, Ph.D., director of the Light Research Program at Thomas Jefferson University in Philadelphia. “LED lights are especially rich in those wavelengths.”

Light, Sleep, and Brain Health

Too much blue light exposure in the evening may affect sleep in several ways. Studies suggest it may decrease sleepiness at bedtime and increase the amount of time it takes to fall asleep. It also may decrease the length of sleep phases thought to help with learning, memory, and mood, as well as brain restoration and recovery.

“During the day when you’re awake, you generate a lot of toxins in the brain,” says Mariana Figueiro, Ph.D., director of the Lighting Research Center at Rensselaer Polytechnic Institute in New York. “At night when you sleep, you basically clear your brain of the toxins you generated during the day. If you’re not sleeping well at night, you’re not giving your brain the time it needs to clean up toxins.” Preliminary evidence suggests poor sleep may contribute to worsening brain function and memory in aging.

To explore this idea further, scientists at Columbia University recently tested amber-tinted, blue-blocking sleep glasses in a small group of adults with insomnia. The blue-blocking glasses significantly improved sleep compared to wearing clear (placebo) glasses in the evening. Another recent study in Norway suggests wearing blue-blocking glasses in the evening, when used in addition to medication, may help those with bipolar disorder recover more quickly during a manic episode.

Light and Cancer

An early clue that exposure to light at night could be problematic came from studies of people working night shifts. “Observational studies have shown an increased risk of cancer, particularly breast cancer, in women doing long-term night shift work,” Brainard says. “Although there are likely multiple reasons for that, one factor is that such women are losing some of the protective effects of melatonin, which is known to have anti-cancer effects.” 

Since 2007, the International Agency for Research on Cancer, which is part of the World Health Organization, has said that night shift work that involves circadian disruption is a probable cause of cancer. Although most evidence links night shift work with increased breast cancer risk, there is also some research suggesting it might be associated with increased risk of prostate and other hormone-sensitive cancers.

While there is no question that energy-efficient lightbulbs, digital books, and smartphones are useful and important advances in technology, we should never stop considering their impact on our health. Our continuous exposure to blue light affects our daily sleep cycles and our long-term well-being, so get more sunlight, cut down on nightly screen time, and enjoy better rest and improved health.

Managing Blue Light at Night

Individuals vary in how sensitive they are to melatonin suppression from light exposure at night. To support better sleep, try one or more of these tips:

Slip on blue-blocking sleep glasses 2 to 3 hours before bedtime. Since glasses go with you, they save you from having to think about every blue light source you might be exposed to in the evening, like your flat-screen TV, smartphone, or even an LED light in your fridge. Choose sleep glasses that block as much blue light as possible, such as those sold at, which block all blue light.

Use low-blue lights at home in the evening. If blue-blocking sleep glasses don’t appeal to you, try changing out the light sources you use in the evening. Rather than bright overhead lights in the bathroom, for example, consider amber nightlights. Or try low-blue bulbs in bedroom lamps.

Filter out blue light from screens at night. Although you can apply physical filters to block blue light from digital screens like laptops and smartphones, an in-expensive option is a software app that filters out blue light. Such apps automatically adjust screen color according to the time of day and your location. Two free apps are f.lux ( and Iris mini (

Don’t over-rely on blue light filtering apps. Mariana Figueiro and her team recently completed a study of the Night Shift mode created to filter out blue light on newer iPads and iPhones. They found that people still had some melatonin suppression despite using Night Shift mode. Figueiro says that although the app filters out blue light, it still exposes users to a lot of other light, especially since people often hold such devices near their faces. This also may decrease melatonin production at night.

Avoid extensive use of digital devicesin the hour or two before bedtime. Besides giving off a lot of light, our beloved smartphones, laptops, and other digital devices can be mentally stimulating. If you like to read before bed, consider a print book rather than reading from a digital device, which research suggests may interfere with sleep when used before bedtime.

Keep your bedroom as dark as possible. If your bedroom is aglow from outdoor street lights, get window treatments with added room darkening features or removable window blackout panels. Alternately, try a sleep mask.

Get plenty of light during the day. “If you are exposed to a lot of light during the day, you are less sensitive to disruption of your circadian system from evening light,” Figueiro says. She advises going outdoors in the morning or at lunchtime, ideally for at least 30 minutes, to help sync your body’s clock. If that’s not possible, Richard Hansler, co-founder of, suggests brightly lighting the room where you get ready or eat breakfast in the morning, perhaps with cool white LED lights.

Marsha McCulloch, MS, RD, is a freelance writer with a special interest in integrative and functional medicine, including environmental health and wellness.

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