FOR ELECTRONIC DEVICES LIKE LAPTOPS, phones, anything with a LED or LCD display, the problem is that they produce a large amount of artificial blue light. Our natural cue to what time of day it is, primarily to know when morning is, is blue light. By exposing ourselves to large amounts of blue light late at night, we are giving our bodies a cue that it’s time actually to wake up instead of go to sleep. This can lead to defects in our circadian rhythm, and it’s been shown that when we have our biological clock out of phase with the natural day-night cycle outside, that can lead to increases in the rates of diabetes, cancer, heart disease, and even depression.
IT DEPENDS ON THE KIND OF DEVICE and how long people are being exposed to it, but there’s clearly a potential for suppressing melatonin in the evening, which is the hormone we start producing a couple of hours prior to bedtime. Melatonin is essentially a nighttime or darkness signal, telling us it’s time to go to bed. So, if you delay the onset of that signal in the evening, by being exposed to too much light coming from those devices, you may be delaying sleep times. Then, if you have a fixed wake up time and can’t sleep in to compensate, you are experiencing sleep deprivation. Even if you filter the light of the display or somehow protect yourself from it, it may be just as bad, because you’re still depriving yourself of sleep by staying awake to use the device.
Sleep deprivation has been linked to a series of things—it’s been shown that after five consecutive days of five hours of sleep instead of eight hours, people can become pre-diabetic or become hungrier. In the short-term, you become sleepier during the day, and you may reduce daytime performance. And then long-term, you may have more serious consequences, such as increased risk for obesity, diabetes, cardiovascular disease, and even increased risks of cancer. I’m not saying that these self-luminous displays cause cancer. But you want to minimize disruption of circadian rhythms and the curtailment of sleep as much as possible.