You probably know the feeling of drifting off to sleep, only to detect through heavy eyelids that the bedroom has suddenly lit up. A second later, you hear a startling rumble. Your trusty iPhone has just notified you of a text message from a friend who clearly has not gone to bed yet. You might roll over and ignore it, or maybe you pick it up and read the text. But the damage is already done. You’ll have trouble going back to sleep immediately.
Cell phones are wreaking biological havoc on people’s sleeping patterns. Most mobile devices have LED screens, which emit a blue wavelength of light that suppresses the body’s melatonin level. Melatonin is the hormone in human bodies that calms and prepares us for sleep. It is released in darkness, as nighttime approaches. The opposite of melatonin is cortisol, the hormone that primes us for action, and is triggered by light.
“Light is like a drug, except it’s not a drug at all,” neurologist George Brainard told the New York Times. He is one of the first researchers to study the circadian rhythm and the effect of light on the human body. Dr. Brainard did an experiment at the University of Basel in Switzerland. Thirteen men sat in front of a computer for five hours each evening before bed. For one week, they looked at an old-style fluorescent monitor that emitted light composed of several colours from the visible spectrum. For another week, they looked at an LED (light-emitting diodes) screen, which was twice as blue as the old-style monitor. For those who watched the LED screens, it took far longer for melatonin levels to rise, and that deficit remained throughout the night.
In another experiment, the same team compared incandescent and fluorescent bulbs. The latter was modified to emit more blue light. People exposed to fluorescents produced 40 percent less melatonin and felt more awake an hour after lights were turned off.
Because humans are now inundated with light at all hours of the day, particularly well beyond dusk, it’s disrupting our sleep and potentially causing disease. Most basically, it’s screwing with our evolutionary programming. And yet the world is full of blue light. The NY Times reported 1.6 billion new computers, televisions, and cellphones were sold in 2013 alone, and all of those screens light up our homes.
Dr. Brainard hopes that a new generation of screens will someday be developed with wavelenths that adjust to the time of day. Until that happens, though, people need to cut back on their device use in the evenings. Not only will it improve sleep quality (resulting in better health, lower weight gain, less stress, more resistance to seasonal depression), but it also creates the opportunity to do something else – connect with family, have a face-to-face conversation, develop a hobby, read a paperback, or spend time alone in thought. Invest in an old-fashioned alarm clock and leave that phone downstairs until morning. It won’t kill you; it just might save you.