How Does Blue Light Impact Our Sleep Cycle?

These days, it seems like everyone is talking about sleep and blue light. But exactly how and why does blue light disrupt your sleep cycle?

Here’s a look at the mysterious secrets of blue light that scientists are unlocking:

What Is Blue Light?
Just as the name suggests, blue light is light on the visible spectrum that appears blue to the human eye. With a short wavelength of 450-495 nanometers, blue light, also known as high energy visible light, is less filtered and therefore brighter than other light. As a result, brighter blue light has become a staple of artificial lighting – which is where your potential sleep problems begin.

How Do Your Eyes Perceive Blue Light?
Until recently, it was believed that your eyes processed light entirely via rods and cones, two types of photoreceptors in your retina. In the early 90s, however, a study found something new: Exposure to light was disrupting the sleep rhythms of people who were completely blind. How? Part of the answer was found in 1998 with the discovery of ganglion cells, a previously unknown third photoreceptor that responds to blue light.

And just what those ganglion cells are doing with that blue light is literally eye opening.

Melanopsin and You
The photopigment in ganglion cells is called melanopsin. Melanopsin reacts to light in the blue part of the spectrum, which triggers electrical signals to your brain. These nerve impulses have three known primary functions: synchronizing the circadian rhythms which regulate your sleep patterns; regulating and suppressing your body’s production of melatonin, a hormone which also helps dictate your sleep patterns; and controlling pupil size and other mechanisms which help your eyes respond to light.

So essentially, when your eyes absorb blue light from artificial sources late at night, your body is tricked into thinking it’s not yet time for bed.

“I’m pretty sure that at least many of the sleep disorders we are facing epidemically are related to evening or nighttime light,” Dieter Kunz, director of the Sleep Research and Clinical Chronobiology Research Group at Charité–Universitätsmedizin Berlin, told the scientific journal Environmental Health Perspectives.

And that’s backed up by a growing body of scientific fact. For instance, studies have shown that exposure to even moderate amounts of blue light can suppress the production of melatonin for a half hour or more, leading to difficulty sleeping and delaying the onset of vital REM sleep. Of course, blue light itself is not inherently bad; in fact, it’s vital for regulating sleep patterns and can help stimulate brain activity during daylight hours.

But when it comes to getting a good night’s sleep, it turns out that sometimes you really can have too much of a good thing.

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Source: https://www.essilor.co.za/how-does-blue-light-impact-our-sleep-cycle