Average mid-sleep time as a proxy for circadian phase

Abstract

Assessments of circadian phase using melatonin are laborious. Sleep-time indices allow for less laborious phase calculations, but common indices weakly represent melatonin phase. We show how a single sleep-time assessment can represent melatonin phase by over 60%, improving the use of subjective sleep to mirror objective circadian phase.

Keywords: Morningness-Eveningness Questionnaire (MEQ); Munich ChronoType Questionnaire (MCTQ); chronotype; dim-light melatonin onset (DLMO); mid-sleep.