... and what that has to do with your sleep.
Fact: Blue light delays your body clock
In other words, this means that you won't go to bed as early as you normally would if you are exposed to blue light at night.
You see, your body is entrained to a 24-hour sleep cycle (unless, it isn't! However, let's save that for another post). What that means is that your circadian rhythm is set to 24 hours. Moreover, your circadian rhythm regulates your sleep/wake cycle -- basically, when you feel alert and when you feel drowsy.
(By the way, other names for your circadian rhythm include your internal clock, body clock, or biological clock.)
The thing is that your circadian rhythm is sensitive to cues in your environment such as light, among other things. Sunlight is rich in blue light, and this light is an external cue that helps your internal clock stay on track.
So, if daylight is blue light and it cues when it's daytime, then we really shouldn't use blue light at night.
Enter blue-light filters, glasses, and human-centric lighting.
A major source of blue light is fluorescent and LED lighting, with the latter used in mobile phones, tablets, televisions, laptops, etc. To offset this blue light at night, use filters that emit an amber glow. For instance, you can use a filter, such as f.lux, for your laptop screen. You can also turn on the night mode on your mobile or install an app. I personally use night mode as well as an app called Blue Light Filter - Night Mode, Night Shift. There are others that you can find and might consider using as well.
However, remember that your mobile will still emit some blue light even with a filter and that other sources of blue light are commonplace. Because of these situations, amber-coloured glasses were designed to filter out blue light and provide a more comprehensive solution for those who need to work at night.
One technology that is gaining attention from research and corporations is human-centric lighting, designed to take into account the circadian rhythm. However, this innovation has not yet been fully tested. Russell Foster, a leading sleep and circadian researcher, has cautioned that more research must still be conducted before this technology is implemented on a wide scale.
If sleep optimization is your aim, the best course of action would be to avoid blue light altogether. So, consider turning off your devices, lighting some candles, and winding down your day with an evening relaxation ritual. Not only is this good for your circadian rhythm, it's soothing for the soul.
If that's not possible, then supplant blue light with a soft amber glow.