The full spectrum of visible light is often described using the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. TheLEDscreens of TVs, computers, smartphones, and video games produce lots of blue light.
Exposure to high levels of that light close to bedtime can suppress the production of the sleep-promoting hormone melatonin by the brain’s pineal gland, says Charles Czeisler, M.D., chief of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital in Boston. That’s why he and other experts advise that it’s best to avoid staring into computer screens and smart phones 2 or 3 hours before you hit the pillow.
Blocking the Blue Light
For those who can’t—or won’t—unplug in the evening, several companies offer blue blockers, which are glasses that filter out the wavelengths in the blue part of the spectrum. A small 2014 study of Swiss teen boys in the Journal of Adolescent Health found that those who wore blue blockers while using a computer in the few hours before bedtime were significantly more sleepy than the boys who wore clear lenses.
That could be because the glasses “are trying to suppress the intensity of the tremendous amount of blue light emitted from computer screens,” Czeisler says. “The screen you see glowing would actually look like a floodlight” if the human eye were capable of perceiving those wavelengths of blue-enriched light, he says.
Still, he cautions that for blue blockers to offer substantial benefit, they need to block almost all blue light. In addition, he says more research needs to be done to prove that people who wear blue blockers actually fall asleep faster.