The Truth About Blue Light: Just How Harmful Is It?

When winding down from a day spent at work in front of the computer, many people watch television, read an ebook, or scroll through their phone in bed. All those activities mean exposure to blue light, which may impact our health in ways we never considered.

What is blue light?

Visible light is made up of all colors, and each color has a different wavelength. Short wavelengths have higher energy and longer wavelengths. Blue light is the shortest wavelength and positioned next to UV light on the electromagnetic spectrum.

“While sunlight is the strongest source of blue light that we are exposed to we are now exposed to much more blue light from artificial sources such as electronic screens and energy-efficient light bulbs,” says Dr. Gary Morgan, a VSP optometrist.

Electronic screens emit a great deal of blue light. “Blue, green and red LEDs are the light source for devices. Those three kinds of LEDs together produce light that looks white, but the blue LED emits much more light than the other sources,” explains Dr. Edward Carome, a light researcher. An iPhone or iPad with retina display emits twice as much blue light as green light, and four times more blue light than red light.

With people spending more time than ever on their phones and devices, and with the push for LED light bulbs, which emit more blue light than incandescent bulbs, people are exposed to an increasing amount of blue light.

The blue light from LED street lights prompted the American Medical Association (AMA) in June to issue guidance for communities on selecting among LED lighting options, urging communities to use “the lowest emission of blue light possible.” The AMA cited the impact of blue light on both vision and sleep as reasons for decreasing the amount of blue light.

The impact of blue light on eyes 

Dr. Christine L. Allison, professor of optometry, Illinois College of Optometry, cautions that it is not yet known how dangerous blue light is to eye health, noting that there has been no conclusive research yet. “We know that rates of cataracts and macular degeneration are increasing in the U.S., but we can’t yet say the increases are due to blue light emitted from devices, since we are also exposed to it every day from the sun,” she explains.

“Good sunglasses and hats are always good recommendations for anyone to protect their eyes while outside. There are a number of lens companies that are making new lenses for glasses to help filter out blue light,” says Allison.

Blue light may have a larger impact on children than adults, but the extent is not yet known. “Kids are likely more susceptible, as their lenses are clearer and their pupils are bigger, which allows more light into the eye and they will be around these devices for longer in their lifetimes,” says Allison. “However, there is no real research to say how this may play out in their future vision.”

As more schools turn to tablets and electronic textbooks, kids will be exposed to increased amounts of blue light. Morgan notes that with shorter arms, kids hold smartphones and tablets closer to their eyes than adults do, which increases the intensity of light from the device reaching the eye.

Many parents, however, are unaware of blue light. A study by VSP found that 58 percent of parents had little to no awareness of blue light and its potential impact, and only 10 percent of parents had taken steps to protect families against blue light.

In addition to eye health, there’s also the issue of comfort. Blue light is out of focus in our eyes and that causes strain. “What we now refer to as digital eye strain is the eye’s constant yet futile attempt to focus blue light when looking at an electronic screen,” says Morgan. A report from The Vision Council states that 65 percent of American experience symptoms of digital eye strain, which include irritated and/or dry eyes, blurred vision, eye fatigue, neck pain, and headaches. Morgan notes that finding goes hand in hand with the finding that 90 percent of Americans use digital devices for two hours or more per day.

The impact of blue light on sleep

Melatonin is a hormone secreted by the pineal gland that influences circadian rhythms. “In addition to being our sleep hormone, melatonin also has a potent anti-cancer effect,” says Morgan.

While all light can negatively impact the secretion of melatonin, blue light has a particularly large impact on production of it and thus on circadian rhythms, according to a Harvard study.

“We do know blue light can cause sleep issues because it can suppress melatonin, so children and adults should definitely not be using devices late into the evening or they may have trouble sleeping,” Allison recommends.

Several studies have found that the use of electronic devices before bedtime suppressed melatonin and “may perpetuate sleep deficiency and disrupt circadian rhythms, both of which can have adverse impacts on performance, health, and safety.”

Teenagers, already known for having circadian rhythms and sleep patterns that are different from adults, experience a particularly dramatic impact on the production of melatonin after exposure to blue light. When exposed to just one-tenth as much light as adults were, the teens actually suppressed more melatonin than the older people, according to a study from the Rensselaer Polytechnic Institute.

“Sleep deficiency from blue light exposure at night has been linked with adverse health consequences, including greater risk of obesity, diabetes, heart disease and stroke,” says Morgan.

Blue light is not all bad. In fact, it has positive effects, including that it regulates sleep and keeps us alert during the day. The increasing amount of exposure and unknown impact, however, are causes for concern. The Harvard Health Letter concludes, “Light at night is bad for your health, and exposure to blue light emitted by electronics and energy-efficient light bulbs may be especially so.”

Taking some small steps to limit one’s exposure to blue light can be wise and there are no detrimental effects to doing so. (Well, some may see shutting down devices before bed as a negative, but it’s safe to say that there will be no ill health effects.)

What can you do to reduce exposure to blue light?

  • Put down your devices and avoid looking at bright screens two or three hours before bedtime. If you like to read before bed, pick up an actual book instead of an e-reader.
  • If you cannot put your devices down before bed, adjust them to limit your exposure to blue light. Apple devices have a Night Shift setting that “automatically shifts the colors of your display to the warmer end of the color spectrum after dark” You can set it to adjust at whatever time you choose. You can find it under “Display & Brightness” in Settings on your Apple device.
  • A similar app, lux, also works for iOS devices and laptops and has just become available for some Android phones.
  • Special lenses for glasses can filter blue light. Morgan says that even people who do not need vision correction can benefit from wearing glasses with lenses that reduce the amount of blue light entering their eyes. “Blue light filtering lenses should be considered the new safety glasses,” he says.
  • Use the lowest wattage equivalent CFL and LED light bulbs, and use lampshades.
  • Consider purchasing special blue-blocking glasses and filters that filter out blue light. Carome, who is also a partner in LowBlueLights.com, advises consumers to be discerning. He says that clear filters are likely ineffective and advising that they should have some color. He adds, “If it doesn’t look strange, it is not blocking blue.”

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