Mouse Study Questions Effects of Blue Light Screens on Sleep
A new mouse study suggests that blue light emitted from cell phones, computers and other devices may not be as disruptive to sleep patterns as previously thought.
In fact, the U.K. researchers say that using dim cooler lights in the evening and bright warmer lights during the day may be beneficial to our health. In other words, twilight is both dimmer and bluer than daylight, they say, and the body clock uses both of these features to determine when to go to sleep and when to stay awake.
They argue that current technologies designed to limit our evening exposure to blue light — for example, by changing the screen color on mobile devices — may therefore be sending us mixed messages. This is because the small changes in brightness they produce are accompanied by colors that more closely resemble the daytime.
The study, published in the journal Current Biology, used specially designed lighting that allowed the team to adjust color without changing brightness. This revealed that blue colors produce weaker effects on the mouse body clock than equally bright yellow colors.
The results have important implications for the design of lighting and visual displays intended to ensure healthy patterns of sleep and alertness.
According to the researchers, our body clocks use a specialized light sensitive protein in the eye to measure brightness, called melanopsin, which is better at detecting shorter wavelength photons. This is why the researchers originally suggested blue light might have a stronger effect.
However, our perception of color comes from the retinal cone cells; and the new study shows that the blue color signals they supply reduce the impact of light on the clock.
“We show the common view that blue light has the strongest effect on the clock is misguided; in fact, the blue colours that are associated with twilight have a weaker effect than white or yellow light of equivalent brightness,” said Dr. Tim Brown from the University of Manchester.
“There is lots of interest in altering the impact of light on the clock by adjusting the brightness signals detected by melanopsin but current approaches usually do this by changing the ratio of short and long wavelength light; this provides a small difference in brightness at the expense of perceptible changes in color.
“We argue that this is not the best approach, since the changes in colour may oppose any benefits obtained from reducing the brightness signals detected by melanopsin. Our findings suggest that using dim, cooler, lights in the evening and bright warmer lights in the day may be more beneficial.”
Source: University of Manchester
Pedersen, T. (2020). Mouse Study Questions Effects of Blue Light Screens on Sleep. Psych Central. Retrieved on February 22, 2020, from https://psychcentral.com/news/2020/01/16/mouse-study-questions-effects-of-blue-light-screens-on-sleep/153121.html