Blue light can impact your sleep and potentially trigger illness, while it is environmentally friendly. The sun was the major source of illumination before the introduction of artificial lighting, and people spent their evenings in relative darkness. Now, in most of the world, evenings are illuminated, and we take for granted our convenient access to all those lumens.
But in all that light, we might be paying a price for basking. Light throws the biological clock of the body at night, the circadian cycle, out of whack. Sleep just fails. Worse, evidence shows that cancer, diabetes, heart disease, and obesity can contribute to the cause.
Not all light colors have the same effect. Blue wavelengths, which are helpful because they improve concentration, response times, and mood during daytime hours, tend to be the most destructive at night. And our exposure to blue wavelengths, particularly after sunset, is growing due to the proliferation of electronics with screens as well as energy-efficient lighting.
Light and sleep
Everyone has slightly different circadian rhythms, but 24 and one-quarter hours are the average duration. The circadian cycle is significantly longer for people who stay up late, while the rhythms of earlier birds are shorter than 24 hours. In 1981, Harvard Medical School's Dr. Charles Czeisler demonstrated that daylight keeps the internal clock of a person synchronized with the climate.
Is nighttime light exposure bad?
Some studies indicate a link between nighttime exposure to light, such as working the night shift, diabetes, heart disease, and obesity. That's not evidence that these symptoms are triggered by nighttime light exposure; nor is it clear why it might be bad for us.
A research by Harvard shed a little light on the potential relation to diabetes and likely obesity. The researchers placed 10 people on a schedule that changed the timing of their circadian rhythms gradually. Their blood sugar levels grew, causing them to become prediabetic, and levels of leptin, a hormone that makes people feel full after a meal, fell.
Light exposure suppresses melatonin secretion, a hormone that regulates circadian rhythms. Even dim light may interfere with the circadian rhythm and secretion of melatonin in an individual. Stephen Lockley, a Harvard sleep researcher, states that a mere 8 lux, a brightness level surpassed by most table lamps and about twice that of a night light, has an impact. Light at night is part of why many people do not get enough sleep, says Lockley, and studies have related short sleep, as well as diabetes and cardiovascular issues, to an increased risk of depression.
Effects of blue light and sleep
While the secretion of melatonin can be suppressed by light of any kind, blue light at night does so more powerfully. An experiment comparing the results of 6.5 hours of blue light exposure to green light exposure of equal brightness was performed by Harvard researchers and their colleagues. For almost half as long as the green light, the blue light reduced melatonin and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).
Researchers at the University of Toronto compared the melatonin levels of individuals exposed to bright indoor light who were wearing blue-light-blocking goggles to individuals exposed to normal dim light without wearing goggles in another blue light analysis. The fact that the hormone levels in the two groups were roughly the same reinforces the theory that blue light is a strong melatonin suppressor. It also indicates that if they wore eyewear that blocks blue light, shift workers and night owls might maybe protect themselves. Blue light is filtered by inexpensive sunglasses with orange-tinted lenses, but they often obscure other colors, so they are not ideal for use indoors at night. Glasses blocking out blue light alone will cost up to $80.
LED blue light exposure
If blue light has detrimental health consequences, environmental issues may be at odds with personal health, as well as the search for energy-efficient lighting. These compact fluorescent lightbulbs and LED lamps are much more energy-efficient than the old-fashioned incandescent lightbulbs with which we grew up. But they appear to emit more blue light as well.
It is not possible to change the physics of fluorescent lamps, but coatings may be within the bulbs so they create a warmer, less blue light. LED lights are more powerful than fluorescent lights, but in the blue spectrum, they still emit a reasonable amount of light. Richard Hansler, a light researcher at Cleveland's John Carroll University, states that some blue light, but less than most fluorescent lightbulbs, is also emitted by ordinary incandescent lights.
Protect yourself from blue light at night
For night lights, use soft red lights. It is less likely that red light can alter the circadian rhythm and inhibit melatonin.
Starting two to three hours prior to bed, stop staring at bright screens.
Then try wearing blue-blocking glasses or downloading an app that filters the blue/green wavelength at night if you work a night shift or use a lot of mobile devices at night.
Expose yourself during the day to plenty of bright light, which will increase your ability to sleep at night, as well as your mood and alertness during daytime.