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Updated: Feb 6, 2026

Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
Published on: April 7, 2020
Late bedtimes prevent circadian phase advances to morning bright light in adolescents
Stephanie J Crowley1, Chelsea L Fournier1, Charmane I Eastman1
1a Biological Rhythms Research Laboratory, Department of Behavioral Sciences , Rush University Medical Center , Chicago , IL , USA.
Abstract:
We examined phase shifts to bright morning light when sleep was restricted by delaying bedtimes. Adolescents (n = 6) had 10-h sleep/dark opportunities for 6 days. For the next 2 days, half were put to bed 4.5 h later and then allowed to sleep for 5.5 h (evening room light + sleep restriction). The others continued the 10-h sleep opportunities (sleep satiation). Then, sleep schedules were gradually shifted earlier and participants received bright light (90 min, ~6000 lux) after waking for 3 days. As expected, sleep satiation participants advanced (~2 h). Evening room light + sleep restriction participants did not shift or delayed by 2-4 h. Abbreviations: DLMO: dim light melatonin onset.
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