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Melatonin Suppression by Light in Humans Is More Sensitive Than Previously Reported
Garen V Vartanian1, Benjamin Y Li2, Andrew P Chervenak2
1Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA Graduate Program in Macromolecular Science & Engineering, University of Michigan, Ann Arbor, Michigan, USA.
Abstract:
The retina drives various non-image-forming photoresponses, including circadian photoentrainment and pupil constriction. Previous investigators showed that in humans, photic suppression of the clock-controlled hormone melatonin is most sensitive to 460-nm blue light, with a threshold of ~12 log photons cm(-2) s(-1). This threshold is surprising because non-image-forming vision is mediated by intrinsically photosensitive retinal ganglion cells, which receive rod-driven synaptic input and can respond to light levels as low as ~7 log photons cm(-2) s(-1). Using a protocol that enhances data precision, we have found the threshold for human melatonin suppression to be ~10 log photons cm(-2) s(-1) at 460 nm. This finding has far-reaching implications since there is mounting evidence that nocturnal activation of the circadian system can be harmful.
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