Twenty years ago there were concerns about electromagnetic radiation from old-fashioned computer monitors, so much so that many experts suggested sitting at least an arm’s length away. That’s no longer an issue with today’s computers. But the LED backlit screens now on most computers, including tablets (such as the iPad and Kindle Fire) and smartphones, as well as many flat-screen TVs, emit something else, albeit of lesser concern: blue light. As people spend more and more hours using these devices, especially at night, the blue light may interfere with their sleep.
Blue light and your sleep
Exposure to light through the eyes helps regulate the body’s sleep/wake cycle by affecting the pineal gland’s secretion of melatonin. This hormone is produced at night and promotes drowsiness. Exposure to light, notably blue light, suppresses it. This is one way sunlight contributes to alertness, and why lack of light at night helps increase sleepiness.
The potential problem is that LED screens produce enough blue light that, when the devices are used close to bedtime, they can greatly reduce melatonin and increase alertness, and thus delay the onset of sleep and reduce deep sleep. And the less sunlight you get during the day, the more sensitive you become to the melatonin-suppressing effects of light at night.
Computer work or games can interfere with sleep simply because they are stimulating. So researchers have compared the effects of doing exciting or boring tasks on LED screens or on old-style screens (as well as on bright LED screens versus darker ones) before bedtime. At least a few small, short studies have found that bright LED screens have the biggest effect on melatonin production, alertness and/or sleep onset and quality, particularly when stimulating tasks are done on them.
Research on blue light and its effect on sleep (and health in general) is in its infancy. More needs to be done to determine which LED screen variables affect sleep most—for instance, the brightness and size of the screen, your distance from it, when and how long you use it, your sensitivity to blue light and so on. And, of course, the effects depend greatly on what you’re doing on the computer.
Bottom line: If you’re having sleep problems and use a device with an LED screen a lot before bedtime, try using it earlier, or at least dim it as much as possible (in a dark room even a dimmed screen appears quite bright). One basic “sleep hygiene” step is to use your bed only for sleep. That means not using your device in bed, especially if you’re very sensitive to blue light. Try to reserve the hours before bedtime for calming, low-key activities, perhaps reading a paper book. There are special amber-tinted eyeglasses that block blue light, but there’s no clinical evidence showing that they improve sleep. You could also try low-dose melatonin at bedtime, but only for occasional use.