April 21, 2015
Blue Light Has a Dark Side
Are you concerned about the long-term effects of working on a computer all day and what it does to your eye health? Wonder if looking at screens damage your eyesight?
Are you concerned that your kids are spending hours and hours on electronic devices including smart-phones, tablets, laptops and LED screens? What is this doing to their long term eye health and their sleep patterns?
In the United States, the number one cause of blindness is age related macular degeneration. Although genetics, smoking and nutrition are some causes, we know that UV light and especially high energy light can be a risk factor. Blue light consists of wavelengths of high energy which can be absorbed in the back of the eye and potentially cause vision damage long term.
A recent Harvard study is paraphrased below and it sheds some “light” on this topic that affects parents and children every day.
Light at night is bad for your health, and exposure to blue light emitted by electronics and energy-efficient lightbulbs may be especially so.
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 electronic devices pretty much for granted.
Long Term Effects of Staring at Screens
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.
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.
Blue Lights and Sleep
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.
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.
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.
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.
While light of any kind can suppress the secretion of melatonin, blue light 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. Lenses with yellow lenses block blue light, but they also block other colors, so they’re not suitable for use indoors at night.
Protecting Yourself From Excessive Blue Light Exposure
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. Ordinary incandescent lights also produce some blue light, although less than most fluorescent lightbulbs.
There are things you can do to help, including:
- Use dim red lights for night lights. Red light has the least power to shift circadian rhythm and suppress melatonin.
- If you have a family history of macular degeneration, and you are Caucasian or Asian, then stay away from smoking, eat a healthy diet of vegetables and fruits, and protect your eyes from the sun with 100% UV protected sunglasses and blue-blocking lenses should be used when working on a computer, tablet, or smartphone.
- Avoid looking at bright screens beginning two to three hours before bed.
- 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.
- If you work a night shift or use a lot of electronic devices at night consider wearing blue-blocking glasses such as Bluetec lenses. Ask your doctor at Vision Center, P.C. for more info on what lenses will work for you.