Circadian rhythms of early morning awakening insomniacs

Early morning awakening insomniacs exhibit significant phase advances of 2-4 hours in their temperature and melatonin rhythms compared to good sleepers.

• Circadian rhythm phase delays are associated with sleep onset insomnia.
• The study compared early morning awakening insomniacs with age-matched good sleepers.
• Endogenous core body temperature and urinary melatonin rhythms were evaluated during a 24-hour bed rest session.
• Insomniacs showed 2-4 hour phase advances in their temperature and melatonin rhythms.
• The sleepiness rhythms did not show significant phase advances, possibly due to variability in measurement.

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