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Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
Published on: April 7, 2020
Racial differences in the human endogenous circadian period
Mark R Smith1, Helen J Burgess, Louis F Fogg
1Biological Rhythms Research Laboratory, Department of Behavioral Sciences, Rush University Medical Center, Chicago, IL, USA.
Plos One
|July 1, 2009
Summary
African Americans exhibit shorter intrinsic circadian clock periods (tau) and distinct circadian rhythm responses compared to other races. These findings impact understanding of sleep disorders and adaptation to jet lag and shift work.
Area of Science:
- Chronobiology
- Human Physiology
- Sleep Medicine
Background:
- The human circadian clock's endogenous period (tau) influences daily rhythms and individual differences in sleep timing (morningness-eveningness).
- Previous research established tau measurement methods and average values around 24.2 hours.
Purpose of the Study:
- To investigate potential racial differences in the endogenous period (tau) of the human circadian clock.
- To examine racial variations in circadian rhythm's response to phase-shifting protocols.
Main Methods:
- Subjects lived under an ultradian light/dark cycle for 3 days to determine tau.
- Circadian phase assessments were performed before and after the ultradian cycle.
- Racial differences in response to simulated jet lag (phase advancing and delaying) protocols were analyzed.
Main Results:
- African American subjects demonstrated a significantly shorter tau compared to subjects of other races.
- African American subjects exhibited larger phase advances and smaller phase delays in response to light stimuli than Caucasian subjects.
Conclusions:
- Significant racial differences exist in human circadian clock period and phase-shifting responses.
- These findings have implications for personalized sleep disorder treatment, jet lag adaptation, and shift work management.
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