In a 2013 study, researchers asked 30 volunteers to hang out in a sleep lab for three nights each. There, they were exposed to two hours of light before bedtime, either from a standard incandescent lightbulb, a white compact fluorescent bulb, or a blue-enriched compact fluorescent bulb. Sure enough, when the volunteers were exposed to the blue light, their sleep wasn't as deep as it was when they were exposed to the other two lights.
But the light they were exposed to wasn't even that bright: It was around 30 lux, less than the average brightness of a family living room. Other studies have found that it doesn't even take that much blue light to have an effect on your melatonin: A pure blue LED light only takes 9 lux to suppress melatonin secretion by 25 percent.
That begs the question: How bright is the average screen? That depends; at about 9 inches from your face, an iPhone 6 and a MacBook Air both glow at about 60 lux, but an iPhone X blazes at more than 100 lux. When it comes to melanopic lux — the amount of blue light that actually affects your melanopsin cells — most smartphones are bright enough to shift your sleep schedule by an hour or more.
So what should you do to keep your sleep schedule on track? Well, if you don't want to put your devices away two hours before bedtime, there's another option: blue-light-blocking glasses. In a 2009 study, people who wore blue-blocking lenses for three hours before bedtime over two weeks experienced improved sleep quality and an improvement in mood.
Want to try some for yourself? We recommend Blokz blue blocker lenses from Zenni. While traditional blue-blocker lenses are amber or yellow in color, Blokz are made with a blue-blocking polymer that's virtually clear, yet still prevents blue light and UV rays from passing through the lenses. You can add them to any pair of Zenni glasses — just click here to get started.