Re: Revisiting the alerting effect of light; a systematic review

This letter is regarding my concerns about a paper by Xu and Lang entitled "Revisiting the alerting effect of light; a systematic review" that is published in Sleep Medicine Reviews [1]. The authors have tried to address the factors that influence the alerting effect of light. They reported that not only circadian rhythm (Process C) and homeostatic sleep pressure (Process S) affect the alertness levels, a third process which receives sensory inputs from body systems is involved in the alerting effect of light.

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