The idea that our electronic devices are keeping us awake and ruining our sleep is pretty widely accepted—and one common remedy is to alter the screen so it gives off a warm, yellow light. But new research from the University of Manchester suggests that might not be the best idea.
Using dimmer, blue-toned lights in the evening and brighter, yellow-toned lights during the day help support our natural circadian rhythm according to a study published in Current Biology. The reason? Yellow light more closely mimics daytime, which the body naturally reads as a signal for waking up.
“We show the common view that blue light has the strongest effect on the clock is misguided,” study author Tim Brown said in a University of Manchester blog post.
Brown and his colleagues set out to analyze how the color of visible light affects the circadian rhythm of mammals. They conducted a series of experiments on mice, exposing them to blue or yellow light, then observing how it affected their activity level and behavior. The results were striking: At equal intensities, blue light produced a noticeably weaker effect on the mice’s activity patterns than yellow light. The yellow light lengthened their circadian rhythm, essentially keeping them awake longer.
Part of the confusion over the effects of blue light stems from mechanics of how we see. Both humans and mice us a light-sensitive protein, called melanopsin, to measure the brightness of light that enters the eye. Melanopsin is more sensitive to blue light than warmer colors, like yellow. The researchers point out that this might explain why scientists initially suggested that blue light from screens would keep us awake. But this new study disproves that idea, and the researchers suggest it’s because our bodies naturally associate blue light with twilight—and bedtime.
Based on their findings, Brown and his team recommend the following: To get a good night’s sleep, stick with bright, warm-colored lighting during the day then transition to dimmer, cool-toned light in the evening.
“Aligning our body clocks with our social and work schedules can be good for our health,” Brown said. “Using color appropriately could be a way to help us better achieve that.”
If you need a guide, just follow the sun.
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