Melatonin, a naturally occurring hormone related to sleep, needs to be released a few hours before bedtime. In a “natural” situation (one without artificial lights), daylight wanes, melatonin is secreted, and a couple of hours later, you’re drowsy and ready to sleep.
Not only does bright light in the evening make it hard for melatonin release, light in the blue end of the spectrum is particularly powerful in suppressing melatonin. If blue light is present, the pituitary won’t let go of melatonin, in order to keep you awake (it’s “daylight”). Unfortunately, this is also the type of light emitted by most electronic devices – any device by Apple, for example, as well as other brands. This includes laptops, PCs, cell phones, tablets, as well as television and even some alarm clocks. By reading the news on your iPad before bed, you’re inadvertently suppressing your endocrine system’s melatonin release.
When I first suggest to my patients that they start by dimming the household lights a couple of hours before bedtime, they sometimes mutter, but know it’s actually pretty do-able. But when I then tell them that using their smartphone, tablet, laptop, and/or TV is messing up their ability to fall asleep easily and to have quality sleep — they often do more than just mutter. It’s understandably a big deal. Turning off one’s devices two hours before bedtime is, sadly, hard to do. But being chronically sleep deprived is harder. (I’ll write in a future post about the effects of sleep deprivation on the brain and mood. You can also read the post I’ve written, “Sleepless? Five Things to Know About Using Melatonin Correctly“.)
Keep in mind that so far, this is about melatonin and sleep onset. Then, of course, factor in the content on those screens that keep your brain and nervous system stimulated.
One more thing: If you think you don’t have a sleep problem because you fall asleep super quickly — think again. One way sleep doctors determine if you’re sleep deprived is to measure how long it takes for you to fall asleep. A sleep onset latency of 0 to 5 minutes is what happens with severe sleep deprivation; 5 to 10 minutes is “troublesome,” 10 to 15 minutes indicates a mild but “manageable” degree of sleep debt, and 15 to 20 minutes is indicative of “little or no” sleep debt. (If you want to read more about sleep debt and other sleepy stuff, take a look at The Promise of Sleep: A Pioneer in Sleep Medicine Explores the Vital Connection Between Health, Happiness, and a Good Night’s Sleep by William Dement and Christopher Vaughan.)