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Sleep problems – If you put your mobile device screen in night mode, nothing may happen

In recent years, it has been thought that the bluish color of the light emitted by screens can disrupt sleep, but the color is not the most important thing.

Vision is a complex process in which photoreceptors in the retina convert light into electrical impulses that are then processed in the brain. Ambient light not only enables us to see, but also influences our sleep-wake cycle through specialized ganglion cells in the retina. These cells react strongly to short-wave light around 490 nanometers, important for our internal clock. What is important is the intensity of the light per wavelength and not the perceived color. A previous study in mice suggested that yellowish light had a greater impact on the internal clock than bluish light. However, in humans, light-sensitive ganglion cells are probably the main mediators of the effect of light on the internal clock and sleep.

A study from the University of Basel and TUM examined this phenomenon by exposing 16 volunteers to bluish, yellowish and white light stimuli. The aim was to determine whether the color of light influences the internal clock and sleep. The changes in the internal clock, the time until falling asleep and the depth of sleep were assessed. In contrast to the results in mice No evidence was found that the variation in light color between blue and yellow plays a relevant role in humans’ internal clock or sleep.. This finding supports other research indicating that light-sensitive ganglion cells are most important to the human internal clock.

This study, published in Nature Human Behavior, raises additional questions about whether light color affects sleep under different conditions, such as prolonged exposure or different times of day. It also looks at the effects of light from mobile devices on biological rhythms and sleep and recommends avoiding short-wave light on screens at night.


Effects of calibrated blue-yellow light changes on the human circadian clock, published in Nature Human Behavior.

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