Peek At Science: 2023 August 22

Peak At Science 20230117
Quantum Biology

Peek At Science: 2023 August 22

Your circadian rhythm tells your cells when to run which programs. Light is the most important zeitgeber for your circadian rhythm. This system works independent of your visual system, and is most sensitive to blue light. Do you know what this means for your health?

High Sensitivity of the Human Circadian Melatonin Rhythm to Resetting by Short Wavelength Light

These results demonstrate that the efficacy of light in phase shifting human circadian rhythms is wavelength dependent and that the human circadian pacemaker is more sensitive to short (460 nm) versus long (555 nm) wavelengths of visible light.

The finding that the three-cone photopic system used for image-forming is not the primary mediator of circadian responses to light is consistent with previous studies of totally blind (6,7) and red-green color-blind (17) individuals, who maintain normal circadian phase shifting (7) and melatonin suppression responses to white or green (6,17) polychromatic light exposure.

The wider-ranging implication of the work is the demonstration that lux, the standard unit of illuminance used by the lighting industry and clinical research community, is inappropriate when assessing its effects on the circadian system or on melatonin suppression (36), as lux assumes that the light being measured has the same spectral distribution as the visual three-cone photopic system (λmax 555 nm) (36). Our findings demonstrate this assumption to be inappropriate when relating photic drive to the magnitude of circadian resetting. Future measurement and use of light to treat circadian rhythm sleep disorders should incorporate quantification of wavelength and irradiance in addition to the timing, number and pattern of exposures.

Authors: Lockley, Steven W.; Brainard, George C.; Czeisler, Charles A.

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