In today’s world, late-night exposure to bright lights is one of the most common issues affecting sleep quality; this is often attributed to the widespread use of light-emitting screens. Basically, when you check your phone, tablet, or laptop while lying bed, you’re making it more difficult for yourself to fall asleep, while also reducing your sleep quality.
Why blue light is the main problem
Your devices emit light from all across the visible spectrum, which is the portion of the electromagnetic spectrum that is visible to the human eye. The image below shows the wavelengths of light in the visible spectrum, as well as the wavelengths of ultra-violet light, which falls directly below the spectrum, and infra-red light, which falls directly above it.
Light at the 450-470 nm range (i.e. blue light), has been found to be a strong signal for melatonin suppression.[3,4] Essentially, blue light gives your body circadian input, which tells it that it’s not yet time to go to sleep.[3,5] Overall, light at a shorter wavelength tends to lead to a greater suppression of melatonin production, which is why blue light, which has a relatively short wavelength, is so disruptive. Conversely, red light, which has the longest wavelength (of visible light), is the least disruptive to your ability to sleep.[3,4]
Reducing blue-light exposure
In theory, you want to avoid all types of light as much as possible before going to bed. However, this isn’t really feasible, so the next best thing is to avoid blue light, which is the most detrimental to your sleep quality. One of the best solutions available are apps which filter out blue light emitted from your screens.[7,8] This significantly reduces your blue-light exposure, without requiring any effort on your part (aside from downloading the app). The following are a few recommendations for free, high quality programs which do this:
- For Windows / Mac / Linux: get Flux.
- For Android: get the Twilight app.
- For iOS: there’s a built-in Night Shift mode for this (ever since iOS 9.3).
These programs are all modifiable, so you can select your preferable level blue-light filtering, and set them to start up automatically at a specific time. In addition, an added bonus for using them is that they significantly help with eye strain if you tend to look at screens in a dark environment. Using your laptop with the lights off will be much more comfortable now, and you won’t have to feel like someone is aiming a projector in your eyes you when you look at your phone late at night.
Other sources of blue light
In addition to screens, blue light is emitted by other appliances, most notably fluorescent light bulbs and LED lights. Unfortunately, the light coming from these sources can’t be easily filtered via an app. There are, however, some methods for reducing blue light exposure from these sources:
- Replace these lights where possible.
- Cover them with something that dims them, or only allows red light through (e.g. red, cellophane gift wrap).
- Avoid exposure to such lights as much as possible before bedtime.
The last two points are applicable in general, even if the light source isn’t blue (e.g. incandescent light bulbs). Remember: the closer you are to going to sleep, the less light you want to be exposed to.
Summary and Conclusions
- Exposure to light before bedtime makes it more difficult to fall asleep, and reduces sleep quality.
- Blue light, which is emitted by screens and fluorescence bulbs, has the worst impact on your sleep.
- Avoiding such light can help you fall asleep more easily, and sleep better.
- Apps which filter out blue light from screens can help you do that without much effort.
- You can also replace or cover blue/bright lights where possible, and avoid them before going to bed.