Two neuroscientists discuss how blue light negatively affects health and sleep patterns

In the modern age of technology it is not uncommon to come home after a long day at work or school and blow off steam by reading an e-book or watching television. Lately, however, scientists have been cautioning against using light-emitting devices before bed. Why? The light from our devices is “short-wavelength-enriched,” meaning it has a higher concentration of blue light than natural light—and blue light affects levels of the sleep-inducing hormone melatonin more than any other wavelength.

Changes in sleep patterns can in turn shift the body’s natural clock, known as its circadian rhythm. Recent studies have shown that shifts in this clock can have devastating health effects because it controls not only our wakefulness but also individual clocks that dictate function in the body’s organs. In other words, stressors that affect our circadian clocks, such as blue-light exposure, can have much more serious consequences than originally thought.

To discuss the growing concern Scientific American MIND consulted with Thomas Jefferson University neuroscientist George Brainard, who was among the first researchers to investigate how different wavelengths of light affect the release of melatonin, and Harvard University neuroscientist Anne-Marie Chang, who recently discovered that the effects of light-emitting devices on circadian systems extend beyond evening and into the following morning.

[An edited transcript of the conversation follows]

How did you become interested in the effects of light on sleep?
Brainard: I was interested in the effects of light on animals as a teenager. I never planned to be a scientist—I wanted to be a writer! So I learned more about the topic out of pure curiosity. When I began my career as a journalist, I interviewed researchers on the topic who encouraged me to pursue a career in science. So I returned to school to get my doctorate and studied the effects of different wavelengths and intensities of light on rodents. I have exclusively studied the effects of light on humans for the past 30 years.

Chang: As a graduate student, I researched circadian rhythm disorders resulting from different human sleep patterns, particularly those of early and late sleepers. I became interested in the effects of various aspects of light—such as time of day and duration of exposure—on circadian rhythm, sleep and performance.

How exactly does light affect our circadian rhythms? And how is melatonin involved?
Chang: We have known for quite awhile now that light is the most powerful cue for shifting the phase or resetting the time of the circadian clock. We also know that melatonin is present at low levels during the day, begins being released a few hours before bedtime and peaks in the middle of the night. Past studies have shown that light suppresses melatonin, such that light in the early evening causes a circadian delay, or resets the clock to a later schedule; and light in the early morning causes a circadian advancement, or resets the clock to an earlier schedule.

Brainard: In the 1990s my team performed more than 700 experiments over seven years to measure how different wavelengths of light regulate acute melatonin production. Unexpectedly, we found that humans display a peak sensitivity to light in the blue wavelength region of the spectrum.

Rods and cones [photoreceptors in the eye] could not account for this differential regulation of melatonin production, so we postulated another type of photoreceptor was responsible for mediating such physiological responses. These wavelength-sensitive photoreceptors were identified soon after and are known as melanopsin-containing ganglion cells.

What happens in the body when our eyes are exposed to blue light on electronic devices?
Chang: Recent studies have shown that short-wavelength [blue] light has a greater effect on phase shifting the circadian clock and on melatonin suppression. In 2014 my colleagues and I examined the effects of reading on a light-emitting device compared with reading a printed book. Participants who read on light-emitting devices took longer to fall asleep, had less REM sleep [the phase when we dream] and had higher alertness before bedtime [than those people who read printed books]. We also found that after an eight-hour sleep episode, those who read on the light-emitting device were sleepier and took longer to wake up. In the study all participants had to stop reading and turn off the lights at exactly 10 P.M., even if they did not feel sleepy. At home, I would expect people do not have the motivation to turn off their devices and go to bed, so they would stay up longer and experience even more circadian delay and shorter sleep times. The effects in the real world could actually be even greater.

What about extreme environments in which the body does not experience a normal daily cycle of sunlight and darkness?
Brainard: My research into the clinical applications of light got NASA interested in applying these findings to spaceflight scenarios. When an astronaut leaves Earth, his or her body is operating on a 24-hour light/dark cycle, but the space station orbits Earth every 90 minutes, and astronauts see the sun rise and set each time. This shift in the lighting environment, known as slam shifting, can have many health consequences and inspired my work with NASA on creating light-exposure schedules specifically for astronauts. [Editors’ Note: As a result of this work, NASA will begin implementing a new lighting system onboard the International Space Station next year, designed to improve astronauts’ sleep and waking performance.]

Can the effects of light on melatonin ever benefit the body?
Brainard: My research in the 1980s showed that the effect of light on melatonin secretion has clinical benefits. Since then, light therapy has been shown to be effective in treating several other conditions, including depression, sleep disorders, eating disorders and age-related dementia.

Chang: Short-wavelength light can be applied in different circumstances where you actually want to shift the clock. For example, it could help in the mornings when we need to be at peak alertness or in cases of jet lag when we change time zones abruptly and our circadian clocks get thrown off. People with variable sleep patterns, such as shift workers, could also benefit from using a schedule of short-wavelength light exposure to help realign their circadian clocks.

Finally, the question everyone is wondering about: Do you have any suggestions as to what we can do to reduce our blue-light exposure before bed?
Chang: For those who just cannot turn off digital devices, here are a few suggestions: You can dim the brightness of your devices or you can make use of programs that filter out short-wavelength light in the evening. I’ve also heard of modern technologies that use different settings, such as reversing the print so the page is dark and the text is light, which, though untested, are probably beneficial if they reduce the amount of emitted light. But the best and least popular answer would be to simply avoid your devices before going to sleep!

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By Jessica Schmerler on September 1, 2015

More information from SCIENTIFICAMERICAN

A recent study by Bank of America shows that nearly half of U.S. consumers couldn’t last a day without their mobile devices. It makes sense. Think about the first thing that you do in the morning. If you’re like me, you’re catching up on email before you even get out of bed. Then, you head straight to your computer at work and spend a majority of the day on it or using one of the many other digital devices that are available in today’s increasingly-technological society.

But what if I told you that these electronics are emitting a dangerous blue light, which is negatively impacting not only your vision but also your overall health? It’s true, and it’s a major concern for eye doctors across the country.

First, let me be clear: I love technology, and I fully embrace it. I actually use a tablet and Google Glass (definitely a talking point with my patients!) as part of my exam process, because it allows me to spend more time engaging with my patients instead of having my back to them while I work at a computer. But just as I advise my patients to protect their eyes from the sun, I also advise them to take protective measures for their eyes when using digital devices.

Continual extended screen time can impact your eyes in two major ways. The first and most common side effect is digital eye strain. When we look at a screen, our blink rate drops significantly, and our eyes won’t put up with that for too long without fuss.

If you’ve ever experienced slightly blurry vision after staring at the computer all day, that was a sign of digital eye strain. Maybe your eyes feel dry, runny or tired after scrolling through your Facebook feed, or maybe you get a headache after a few hours on the computer. These symptoms are often so common that we don’t even recognize them as real issues. While digital eye strain is temporary, if left unaddressed, it can turn into a chronic problem.

The easiest way to address digital eye strain is to blink more. That might sound overly simple, but blinking helps to keep eyes lubricated. Another effective way to avoid or help to resolve digital eye strain is to follow the “20-20-20 Rule” — every 20 minutes, stare at something at least 20 feet away for at least 20 seconds. This exercise engages your distance vision and helps the eye to “reset.”

The second — and more serious — impact that too much technology consumption can have on our eyes is damage from blue light exposure. Blue light is just what it sounds like — it’s a type of light that gives off a blue color. Blue light is harmful, because it’s the highest energy wavelength of visible light. This energy is also able to penetrate all the way to the back of the eye, through the eyes’ natural filters, and that’s the problem.
Even though blue light is nothing new, the biggest issue is the amount of blue light exposure that we get each day through digital device use. With this exposure increasing over time, we are actually causing permanent damage to our eyes. But unlike digital eye strain, the effects of blue light are cumulative and can lead to eye diseases like macular degeneration.

Children are especially at risk when it comes to the negative effects of blue light exposure. These days, a lot of homework is done online, and many children have access to (or have their own) digital devices that they are using for increasingly longer periods of time. The difference for children is that their eyes are still developing, and they don’t yet have the protective pigments in their eyes to help filter out some of this harmful blue light. That’s why, just like with UV radiation, most blue light exposure occurs before kids are 18 years old.

While it may be a great concern for children, adults are susceptible, as well. This is especially true as adults are using digital devices more and more in both their personal and professional lives. So what can you do about it?
First, you can take steps to protect your eyes from the harmful effects of blue light. If you’re not able to limit your digital device use, at least cut back on it before bed. Studies show that exposure to blue light a couple of hours before bedtime actually suppresses melatonin and delays deep REM sleep significantly. So cutting back on tech use at night means getting better sleep, making people more productive at both work and school (and speaking from my own personal experience, it makes children more pleasant).

Second, you should consider talking with your eye doctor about lenses that filter out blue light (and no, these aren’t the old bright orange blue-blocker eyewear from the ‘90s). The lenses have little-to-no tint and can help to minimize the direct blue light exposure that you get throughout the day. Most of my patients who have these lenses noticed an immediate increase in eye comfort because of the improved contrast, which helps to relax the eyes. And if you have children, I would absolutely recommend these lenses — especially if they have trouble sleeping at night.

By keeping in mind a few simple ways to protect the eyes, we can take pleasure in knowing that our eyes will last much longer than our trusty smartphones, tablets and computers.

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Exposure to blue light at night, emitted by electronics and energy-efficient lightbulbs, harmful to your health.

Until the advent of artificial lighting, the sun was the major source of lighting, and people spent their evenings in (relative) darkness. Now, in much of the world, evenings are illuminated, and we take our easy access to all those lumens pretty much for granted.

But we may be paying a price for basking in all that light. At night, light throws the body's biological clock—the circadian rhythm—out of whack. Sleep suffers. Worse, research shows that it may contribute to the causation of cancer, diabetes, heart disease, and obesity.

But not all colors of light have the same effect. Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown.

Daily rhythms influenced by light

Everyone has slightly different circadian rhythms, but the average length is 24 and one-quarter hours. The circadian rhythm of people who stay up late is slightly longer, while the rhythms of earlier birds fall short of 24 hours. Dr. Charles Czeisler of Harvard Medical School showed, in 1981, that daylight keeps a person's internal clock aligned with the environment.

The health risks of nighttime light

Study after study has linked working the night shift and exposure to light at night to several types of cancer (breast, prostate), diabetes, heart disease, and obesity. It's not exactly clear why nighttime light exposure seems to be so bad for us. But we do know that exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms, and there's some experimental evidence (it's very preliminary) that lower melatonin levels might explain the association with cancer.

A Harvard study shed a little bit of light on the possible connection to diabetes and possibly obesity. The researchers put 10 people on a schedule that gradually shifted the timing of their circadian rhythms. Their blood sugar levels increased, throwing them into a prediabetic state, and levels of leptin, a hormone that leaves people feeling full after a meal, went down.

Even dim light can interfere with a person's circadian rhythm and melatonin secretion. A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect, notes Stephen Lockley, a Harvard sleep researcher. Light at night is part of the reason so many people don't get enough sleep, says Lockley, and researchers have linked short sleep to increased risk for depression, as well as diabetes and cardiovascular problems.

The power of the blues

While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).

In another study of blue light, researchers at the University of Toronto compared the melatonin levels of people exposed to bright indoor light who were wearing blue-light–blocking goggles to people exposed to regular dim light without wearing goggles. The fact that the levels of the hormone were about the same in the two groups strengthens the hypothesis that blue light is a potent suppressor of melatonin. It also suggests that shift workers and night owls could perhaps protect themselves if they wore eyewear that blocks blue light. Inexpensive sunglasses with orange-tinted lenses block blue light, but they also block other colors, so they're not suitable for use indoors at night. Glasses that block out only blue light can cost up to $80.

Less-blue light

If blue light does have adverse health effects, then environmental concerns, and the quest for energy-efficient lighting, could be at odds with personal health. Those curlicue compact fluorescent lightbulbs and LED lights are much more energy-efficient than the old-fashioned incandescent lightbulbs we grew up with. But they also tend to produce more blue light.

The physics of fluorescent lights can't be changed, but coatings inside the bulbs can be so they produce a warmer, less blue light. LED lights are more efficient than fluorescent lights, but they also produce a fair amount of light in the blue spectrum. Richard Hansler, a light researcher at John Carroll University in Cleveland, notes that ordinary incandescent lights also produce some blue light, although less than most fluorescent lightbulbs.

What you can do

• Use dim red lights for night lights. Red light has the least power to shift circadian rhythm and suppress melatonin.

• Avoid looking at bright screens beginning two to three hours before bed.

• If you work a night shift or use a lot of electronic devices at night, consider wearing blue-blocking glasses or installing an app that filters the blue/green wavelength at night.

• Expose yourself to lots of bright light during the day, which will boost your ability to sleep at night, as well as your mood and alertness during daylight.

More information from Harvard Health Publications

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Visible light is much more complex than you might think.

Stepping outdoors into sunlight; flipping on a wall switch indoors; turning on your computer, phone or other digital device — all of these things result in your eyes being exposed to a variety of visible (and sometimes invisible) light rays that can have a range of effects.

Most people are aware that sunlight contains visible light rays and also invisible ultraviolet rays that can tan or burn the skin. But what many don't know is that the visible light emitted by the sun comprises a range of different-colored light rays that contain different amounts of energy.

What Is Blue Light?

Sunlight contains red, orange, yellow, green and blue light rays and many shades of each of these colors, depending on the energy and wavelength of the individual rays (also called electromagnetic radiation). Combined, this spectrum of colored light rays creates what we call "white light" or sunlight.

THE LIGHT SPECTRUM

Without getting into complicated physics, there is an inverse relationship between the wavelength of light rays and the amount of energy they contain. Light rays that have relatively long wavelengths contain less energy, and those with short wavelengths have more energy.

Rays on the red end of the visible light spectrum have longer wavelengths and, therefore, less energy. Rays on the blue end of the spectrum have shorter wavelengths and more energy.

The electromagnetic rays just beyond the red end of the visible light spectrum are called infrared — they are warming, but invisible. (The "warming lamps" you see keeping food warm at your local eatery emit infrared radiation. But these lamps also emit visible red light so people know they are on! The same is true for other types of heat lamps.)

On the other end of the visible light spectrum, blue light rays with the shortest wavelengths (and highest energy) are sometimes called blue-violet or violet light. This is why the invisible electromagnetic rays just beyond the visible light spectrum are called ultraviolet (UV) radiation.

Key Points About Blue Light

Like ultraviolet radiation, visible blue light — the portion of the visible light spectrum with the shortest wavelengths and highest energy — has both benefits and dangers. Here are important things you should know about blue light:

1. Blue light is everywhere.

2. HEV light rays make the sky look blue.

3. The eye is not very good at blocking blue light.

4. Blue light exposure may increase the risk of macular degeneration.

5. Blue light contributes to digital eye strain.

6. Blue light protection may be even more important after cataract surgery.

7. Not all blue light is bad.

Blue Light Filters And Protective Eyewear

If you are using your phone constantly — especially if you use it primarily for texting, e-mailing and web browsing — a convenient way to reduce your blue light exposure is to use a blue light filter.

Digital electronic devices emit blue light that can cause eye strain and may lead to eye problems over time.

These filters are available for smartphones, tablets, and computer screens and prevent significant amounts of blue light emitted from these devices from reaching your eyes without affecting the visibility of the display. Some are made with thin tempered glass that also protects your device's screen from scratches.

More information from Health.com

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Watch these products to keep away from the blue light and protect your eyes

• iPhone 7 ‧ 7 Plus

• iPhone 6 ‧ 6 Plus / 6S ‧ 6S Plus

• iPhone 5 ‧ 5C ‧ 5S

• iPhone 4 ‧ 4S

• more products