Can blue light-blocking glasses improve your sleep?

Recently, my brother mentioned he was sleeping better since he got new prescription glasses with a blue-light filter. He wears his glasses mostly for reading screens (both computer and smartphone) during the day while at work. So I was intrigued, but a little skeptical: could daytime use of blue light-filtering glasses make a difference in how well he slept? How, when, and why blue light affects us seemed like good questions to pose to an expert before deciding whether those glasses could help me, too.

forrest

What is blue light?

Visible light includes a short segment of wavelengths tucked into the electromagnetic radiation spectrum. Together, the wavelengths of visible light captured by our eyes are translated into white light by our brains.
You may remember looking through a prism to bend the wavelengths that make up white light into a rainbow of colors. At one end of this rainbow, blue light shades toward violet. Sunlight has a lot of light at all visible wavelengths.

Measured in nanometers (nm), visible light wavelengths range from 400 to 700 nm. Blue-light wavelengths lie between about 450 and 495 nm. And different slices of blue-light wavelengths have different effects on our bodies, including on sleep and alertness.

How can blue light affect sleep?

During the day blue-enriched light is desirable, because it helps synchronize our circadian clocks to a 24-hour day. So, exposure to a regular light-and-dark cycle is vital to achieve and maintain good sleep.

Stimulation from certain wavelengths of blue light helps us stay alert, whether this comes from a natural source like the sun in daytime hours, or from electronic devices that emit blue light. While the stimulation is helpful during the day, at night it can interfere with sleep. Blue-light exposure in the evening — for example, binging a TV series on your laptop right before bed — will stimulate the melanopsin-containing cells and alert the brain, making it think it is daytime. That can make it harder to fall asleep and may affect the quality of your sleep.