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Updated: Aug 20, 2026

Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
Published on: April 7, 2020
The relationship between the dim light melatonin onset and sleep on a regular schedule in young healthy adults
Helen J Burgess1, Natasha Savic, Tracey Sletten
1Biological Rhythms Research Laboratory, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL 60612, USA. hburgess@rush.edu
Abstract:
The endogenous melatonin onset in dim light (DLMO) is a marker of circadian phase that can be used to appropriately time the administration of bright light or exogenous melatonin in order to elicit a desired phase shift. Determining an individual's circadian phase can be costly and time-consuming. We examined the relationship between the DLMO and sleep times in 16 young healthy individuals who slept at their habitual times for a week. The DLMO occurred about 2 hours before bedtime and 14 hours after wake. Wake time and midpoint of sleep were significantly associated with the DLMO (r = 0.77, r = 0.68 respectively), but bedtime was not (r = 0.36). The possibility of predicting young healthy normally entrained people's DLMOs from their sleep times is discussed.
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