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Updated: Dec 23, 2025
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Collecting Sleep, Circadian, Fatigue, and Performance Data in Complex Operational Environments
Published on: August 8, 2019
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Sleep and circadian instability in delayed sleep-wake phase disorder
Lauren A Watson1, Elise M McGlashan1, Ihaia T Hosken1
1School of Psychological Sciences and Turner Institute for Brain and Mental Health, Monash University, Melbourne, Victoria, Australia; *Contributed equally.
Summary
Patients with delayed sleep-wake phase disorder (DSWPD) exhibit less stable circadian timing and irregular sleep patterns compared to controls. Increased light sensitivity is linked to circadian instability in DSWPD.
Area of Science:
- Chronobiology
- Sleep Medicine
- Circadian Rhythms
Background:
- Delayed sleep-wake phase disorder (DSWPD) is associated with circadian clock sensitivity to light, potentially leading to unstable rhythms.
- Irregular sleep schedules in DSWPD may exacerbate circadian instability.
Purpose of the Study:
- To investigate the stability of circadian timing and sleep regularity in DSWPD patients.
- To compare circadian stability and sleep patterns between DSWPD patients and healthy controls.
Main Methods:
- Two dim-light melatonin onset (DLMO) assessments were conducted approximately two weeks apart.
- Light sensitivity was measured via phase-resetting response to a 150-lux stimulus.
- DLMO instability was assessed and correlated with light sensitivity and sleep regularity index.
Main Results:
- DSWPD patients displayed later sleep timing, lower sleep regularity, and greater DLMO instability than controls.
- Increased DLMO instability correlated with heightened light sensitivity across all participants.
- This association between instability and light sensitivity was not significant within DSWPD or control groups individually.
Conclusions:
- Circadian timing and sleep regularity are significantly less stable in individuals with DSWPD.
- These findings suggest that circadian instability may contribute to the etiology of DSWPD.
- Assessing light sensitivity could aid in developing personalized DSWPD treatment strategies.
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