Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: No influence of iris color

Conclusions:
A single 2-hour bright light pulse combined with a moderate delay of the sleep/dark episode delayed the circadian clock an average of ~1.5 hours. There was no evidence that iris color influenced the magnitude of the phase shift. Future studies are needed to replicate our findings that iris color does not impact the magnitude of light-induced circadian phase shifts, and that the previously reported differences may be due to race. (Source: Journal of Circadian Rhythms)

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