Almost everyone knows that blue light is disruptive to our sleep cycle, and our favorite devices—laptops, tablets, and smartphones—emit plenty of it. That’s why plenty of people activate their devices’ nighttime modes or banish them from the bedroom entirely when they’re winding down for the evening.
Except blue light isn’t all that bad.
At least, that’s what new research from the University of Manchester suggests. Flying in the face of commonly accepted wisdom, this new study suggests that blue light is not the most disruptive light color to sleep cycles.
Researchers from the University of Manchester tested the effects of various light colors on mice’s body clocks. Importantly, researchers were able to change light colors without altering brightness—implying that any observed disruptions from added light were based on color, not light intensity.
Most people would guess that blue light had the strongest effect on the mice’s circadian rhythms. That’s not what the researchers found, though. Instead, they found that yellow colors affected the mice more than blue colors of equal brightness.
How does that work?
The researchers speculate that, since mice are diurnal animals (aka, they sleep during the night), they likely associate cooler colors with twilight… a prime time to wind down and catch some Z’s. This logic means that warmer colors are conversely associated with daytime, signalling wakefulness. So, this research suggests that brighter, warmer colors can be particularly disruptive at night.
How does this apply to night owls who love their smartphones? Well, it’s still important to reduce light brightness, as it can impact circadian responses regardless of color. Instead, it’s likely better to keep light exposure limited and of lower intensity. And, if choosing light color is an option, cooler colors are the way to go, this study suggests. In other words, opt for dimmer, cooler light colors at night if you can’t part from your device.