Contrary to common belief, blue light may not be as harmful to our sleep patterns as originally thought, according to scientists at the University of Manchester.
According to the team, the use of dim, cooler lights at night and warmer lights in the day may be more beneficial to our health.
Twilight is darker and more blue than daylight, they say, and the biological clock uses both features to determine the appropriate times to be asleep and awake.
Current technologies designed to limit our night exposure to blue light, for example by changing the color of the screen on mobile devices, can send mixed messages, they argue.
This is because the small changes in brightness they produce are accompanied by colors that are more similar to the day.
The research, which was performed on mice, used specially designed lighting that allowed the team to adjust the color without changing the brightness.
That showed that the blue colors produced weaker effects on the mouse's body clock than the equally bright yellow colors.
The results, according to the team, have important implications for the design of lighting and visual screens designed to ensure healthy sleep and alert patterns.
The study is published in Current biology and funded by the Biotechnology and Biological Sciences Research Council.
The body's clock uses a specialized light-sensitive protein in the eye to measure brightness, called melanopsin, which is better for detecting photons of shorter wavelengths.
That's why, according to the team, the researchers originally suggested that blue light could have a stronger effect.
However, our perception of color comes from retinal cone cells and new research shows that the blue signals they supply reduce the impact of light on the clock.
Dr. Tim Brown of the University of Manchester said: "We show the common opinion that blue light has the strongest effect on the clock is wrong; in fact, the blue colors that are associated with twilight have an effect weaker than white or light yellow of equivalent brightness.
"There is much interest in altering the impact of light on the clock by adjusting the brightness signals detected by melanopsin, but current approaches generally do so by changing the ratio of light to short and long wavelength; this provides a small difference in the brightness at the expense of perceptible changes in color. "
He added: "We argue that this is not the best approach, since changes in color can oppose any benefit obtained by reducing the brightness signals detected by melanopsin.
"Our findings suggest that the use of dim, cooler lights at night and bright warm lights in the day may be more beneficial."
"The research has already provided evidence that aligning our body clocks with our social and work schedules can be good for our health. Using color properly could be a way to help us achieve it better."
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