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In a groundbreaking study led by researchers from the University of Basel and the Technical University of Munich (TUM), the impact of different light colors on the human body’s sleep-wake rhythm has been scrutinized. Contrary to previous assumptions, the investigation challenges the purported link between light color and its influence on the internal clock.
Vision, a multifaceted process, deciphers the environment through a combination of light wavelengths. These wavelengths, interpreted as colors and brightness in the brain, contribute to visual perception. Photoreceptors in the retina translate light into electrical signals, ultimately shaping our vision. However, the influence of ambient light extends beyond vision, affecting our sleep-wake rhythm. Specialized ganglion cells, sensitive to light, particularly short-wavelength light around 490 nanometers, communicate daylight to our internal clock. Despite the perceived color, the intensity of light per wavelength is pivotal, overshadowing the relevance of color.
Dr. Christine Blume, from the Centre for Chronobiology at the University of Basel, spearheaded the study, questioning the role of cones—responsible for color perception—on the internal clock. The research delved into contrasting the impact of blueish and yellowish light on sleep and the internal clock.
Contradicting a previous mouse study suggesting yellowish light’s potency in influencing the internal clock, the research exposed 16 healthy volunteers to various light stimuli. These stimuli differentially activated color-sensitive cones while uniformly stimulating light-sensitive ganglion cells. Results indicated no significant correlation between light color variation and alterations in the internal clock or sleep, contrary to prior findings.
According to Blume, “Our study challenges the notion that light color along the blue-yellow spectrum significantly impacts the human internal clock.” Professor Manuel Spitschan, involved in the study, emphasized the predominant role of light-sensitive ganglion cells over color in influencing the internal clock, underscoring the study’s implications for practical lighting design.
However, the study leaves open the possibility that altering parameters, such as duration or timing of light exposure, might yield different outcomes. Additionally, the study’s insights suggest that the short-wavelength component of screens affects biological rhythms, corroborating the advice to limit screen exposure before bedtime or use night shift modes.
While night mode on screens reduces short-wavelength light proportions, the study suggests that modifying this component without color adjustment could still be effective, presenting possibilities for improved technological implementation in mobile phone displays.
