Insomnia and poor sleep quality are common problems, especially for shift workers. Research indicates that part of sleeping poorly is having your circadian clock disrupted. That's the neurological timing mechanism in your brain that makes you sleep and wake at regular times.
It turns out that blue light hitting your eyes sends a signal to your brain that it's time to wake up. If you're looking at blue light before you go to sleep, you'll sleep less well.
In this study, a small but thought-provoking randomized controlled trial, people who wore amber sunglasses (which block blue light) before bedtime had gradually improving sleep over three weeks. They also reported being in better moods. The comparison group just wore glasses that blocked ultraviolet light, and they had no changes in their sleep quality or mood.
The implications of this are widespread, because apart from electrical light being everywhere, people tend to watch television and stare at their computers before they go to bed. All that blue light has to be reducing sleep quality. And the world, it seems, is chronically fatigued.
What to do? There's a are Mac apps (here and here) that reduce the blues and greens on your monitor. Or you could get eccentric, and wear amber sunglasses around the house for a few hours before you go to bed.