April 23, 2024

New Study Finds Light Color Has Minimal Impact On Internal Clock

A recent study conducted by researchers from the University of Basel and the Technical University of Munich challenges the long-held belief that light color significantly affects the human internal clock. The study, published in the journal Nature Human Behaviour, focused on the effects of different light colors on the internal clock and sleep.

Vision, the process through which our environment is perceived, involves the interpretation of various wavelengths of light. Photoreceptors in the retina convert light into electrical impulses, which are then transmitted to ganglion cells in the retina. These ganglion cells are particularly sensitive to short-wavelength light at around 490 nanometers, which signals to the internal clock that it is daytime.

Previous research suggested that yellowish light may have a stronger influence on the internal clock than bluish light. However, the new study challenges this notion and investigates the role of light color, specifically the cones in the retina that encode light color, on the internal clock.

To study this, the researchers exposed 16 healthy volunteers to either bluish or yellowish light stimuli for one hour in the late evening, as well as a white-light stimulus as a control condition. They designed the light stimuli to differentially activate the color-sensitive cones in the retina. The stimulation of the light-sensitive ganglion cells, which are the main drivers of the internal clock, remained the same across all three conditions.

The researchers then analyzed the effects of the different light stimuli on the participants’ internal clocks, sleep onset, sleep depth, tiredness, and reaction time. The results showed no evidence that the variation of light color along a blue-yellow dimension plays a relevant role in the human internal clock or sleep. This contradicts previous findings from a mouse study.

The study’s lead author, Dr. Christine Blume, emphasizes the importance of considering the impact of light on the light-sensitive ganglion cells when planning and designing lighting. She states that the cones and the color of light play a very minor role in this regard.

While the study provides valuable insights into the effects of light color on the internal clock, further research is needed to investigate whether different parameters, such as the duration and timing of light exposure, may yield different results. Additionally, the study addresses concerns about the impact of short-wavelength light from smartphone and tablet screens on sleep. The recommendation to avoid using these devices late in the evening or to enable night shift mode, which reduces short-wavelength light proportions, is supported by Dr. Blume.

In conclusion, the study challenges the notion that light color significantly affects the human internal clock. The findings highlight the importance of considering the impact of light on the light-sensitive ganglion cells and suggest that the color of light may have minimal relevance. As technology continues to evolve, further research and technological advancements may provide additional insights into optimizing lighting and minimizing potential disruptions to the internal clock and sleep patterns.

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1. Source: Coherent Market Insights, Public sources, Desk research
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