Smartphone “night mode” may interfere with sleep due to adverse effects
Recent smartphonesNight Shift”Function is installed, and at nightBlue lightBy reducing the color of the screen, the color of the screen becomes a warmer yellowish color, reducing the burden on the eyes. However, an experiment conducted by a research team at the University of Manchester has raised the possibility that “ Blue light has no effect to disturb sleep as widely thought, and yellowish light has a greater influence on sleep ''. .
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The melanopsin photoreceptor in optic nerve cellsCircadian rhythmIt is known to be deeply involved in the regulation of Melanopsin is a hormone that detects the length of light by detecting the brightness of light that enters the eye and synchronizes biological functions with circadian rhythms.MelatoninTo secrete.
According to Brown, the melanopsin system is excellent at detecting short-wavelength light, and has been thought to be particularly sensitive to blue light, which has a short wavelength, among visible light. Normally, the amount of melatonin secretion decreases during the day and increases at night, but when you look at the blue light at night, the melanopsin is judged to be “daytime” and the secretion of melanopsin is suppressed. It is supposed to end up. From this point, the idea of reducing the blue light from the screen so as not to disturb the circadian rhythm was “based on a scientifically valid idea,” says the University of Manchester.Timothy BrownDr. says.
However, it is not only melanopsin that reacts to color, but also a type of photoreceptor that has been known for a long timeCone cellsAlso plays an important role in human perception of color. Therefore, Mr. Brown's research team conducted an experiment to investigate how the intensity and color of the light applied to the mouse affects the circadian rhythm using lighting that can freely change the brightness and color of the lighting. I did it.
As a result of analyzing the effects of various light conditions on the circadian rhythm of mice, it was found that the intensity of the luminance was greater than the shade of light. In addition, when the brightness is the same, it seems that yellowish warm colors have a greater influence on the circadian rhythm than bluish light with a lot of blue light.
“Our common perception that blue light has the strongest influence on the body clock is wrong. In fact, a bluish light similar to that at dusk is a white or yellow light of the same brightness. "It has less impact on the body clock." Because the light at sunset is darker and bluish than the daytime light, the color of the screen seen at night is as blue as at sunset, it may be difficult to disturb the circadian rhythm . In contrast, white and yellowish screen colors close to daylight can disrupt circadian rhythms.
The existing night mode is based on the idea of adjusting the wavelength of the light emitted by the screen and reducing the effect of blue light on melanopsin. On the other hand, the screen color change affects not only the melanopsin but also the pyramidal cells, so the demerit of the color change may outweigh the benefits gained from the reduction of blue light. Brown argues that the approach is not the best.
At the time of writing, the research results were derived from mouse experiments, but “we believe there are good reasons for this to apply to humans,” commented Brown. Rather than paying attention only to the color of the screen, more fundamental measures such as “Do not use a smartphone before going to sleep” are considered to be certain.