A five-primary VDU demonstrated a 3× adjustment in while maintaining the same visual appearance.
Self-reported sleepiness and salivary melatonin levels increased significantly during VDU exposure, consistent with expected diurnal patterns.
Reducing melanopic-irradiance enhanced the magnitude of increases in both sleepiness and melatonin levels.
Melatonin onset and sleepiness can be modulated independently of visual characteristics such as color and brightness.
Simplified
OBJECTIVES: Artificial light sources such as visual display units (VDUs) elicit a range of subconscious and reflex light responses, including increases in alertness and suppression of pineal melatonin. Such responses employ dedicated retinal circuits encompassing melanopsin photoreceptors. Here, we aimed to determine whether this arrangement can be exploited to modulate the impact of VDUs on melatonin onset and alertness without altering visual appearance.
METHODS: We generated a five-primary VDU capable of presenting metameric movies (matched for color and luminance) but varying in . Healthy human participants (n = 11) were exposed to the VDU from 18:00 to 23:00 hours at high- or low-melanopic setting in a randomized cross-over design and measured salivary melatonin and self-reported sleepiness at 30-minute intervals.
RESULTS: Our VDU presented a 3× adjustment in melanopic-irradiance for images matched photometrically for color and luminance. Participants reported no significant difference in visual appearance (color and glare) between conditions. During the time in which the VDU was viewed, self-reported sleepiness and salivary melatonin levels increased significantly, as would be expected in this phase of the diurnal cycle. The magnitude of the increase in both parameters was significantly enhanced when melanopic-irradiance was reduced.
CONCLUSIONS: Our data demonstrate that melatonin onset and self-reported sleepiness can be modulated independent of photometric parameters (color and luminance) under a commonly encountered light exposure scenario (evening use of a VDU). They provide the first demonstration that the impact of light on alertness and melatonin production can be controlled independently of visual experience, and establish a VDU capable of achieving this objective.
Key numbers
3×
Increase in
varied by a factor of 3 under matched color and luminance conditions.
11 of 11
Participants Reporting Increased Sleepiness
Self-reported sleepiness increased significantly under low-melanopic settings.
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