The color of light is less important for sleep than expected
Published: Friday, Dec 22nd 2023, 11:20
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The color of light is less important for sleep than previously assumed. As a research team from the University of Basel has shown in a new study, people sleep equally well whether they are exposed to yellow or blue light in the evening.
The starting point for the study, published on Friday in the journal Nature Human Behaviour, was a 2019 study on mice, which suggested that yellowish light has a stronger influence on the circadian clock than bluish light, as Christine Blume from the University of Basel explained to the Keystone-SDA news agency.
Based on the results of this study four years ago, many concluded that the night mode of smartphones could have negative effects on sleep. This is because it makes the colors of the display appear yellowish. The new findings of the researchers from Basel contradict this.
However, the night modes of smartphones could be designed differently, explained Blume. According to Blume, changing the color spectrum would not be necessary. "That's a side effect. Technologically, it would be quite possible to reduce the short-wave light component even without color adjustment," said the sleep researcher.
Study in the sleep laboratory
In their study, the researchers from the University of Basel and the Technical University (TU) of Munich compared the influence of different light colors on the human body, as the University of Basel explained in a press release. The researchers exposed 16 test subjects to a bluish or yellowish light stimulus for one hour in the late evening, as well as a white light stimulus as a control condition.
The light stimuli were designed in such a way that although they activated different cones, which are responsible for color vision, they always stimulated the so-called ganglion cells in the same way. Ganglion cells are nerve cells that collect information from the photoreceptors and transmit it to the brain via the optic nerve. This made it possible to determine the role of light color independently of other factors.
In the sleep laboratory, they determined whether the color of the light altered the internal clock of the test subjects, how long it took them to fall asleep and how deep their sleep was at the beginning of the night. They also asked about their tiredness and tested their ability to react, which decreases with increasing sleepiness. They found no evidence of changes in these factors with the different types of light, as the study shows.
©Keystone/SDA
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