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Later endogenous circadian temperature nadir relative to an earlier wake time in older peopleThe contribution of the circadian timing system to the age-related advance of sleep-wake timing was investigated in two experiments. In a constant routine protocol, we found that the average wake time and endogenous circadian phase of 44 older subjects were earlier than that of 101 young men. However, the earlier circadian phase of the older subjects actually occurred later relative to their habitual wake time than it did in young men. These results indicate that an age-related advance of circadian phase cannot fully account for the high prevalence of early morning awakening in healthy older people. In a second study, 13 older subjects and 10 young men were scheduled to a 28-h day, such that they were scheduled to sleep at many circadian phases. Self-reported awakening from scheduled sleep episodes and cognitive throughput during the second half of the wake episode varied markedly as a function of circadian phase in both groups. The rising phase of both rhythms was advanced in the older subjects, suggesting an age-related change in the circadian regulation of sleep-wake propensity. We hypothesize that under entrained conditions, these age-related changes in the relationship between circadian phase and wake time are likely associated with self-selected light exposure at an earlier circadian phase. This earlier exposure to light could account for the earlier clock hour to which the endogenous circadian pacemaker is entrained in older people and thereby further increase their propensity to awaken at an even earlier time.
Document ID
20040142196
Document Type
Reprint (Version printed in journal)
Authors
Duffy, J. F. (Brigham and Women's Hospital and Harvard Medical School Boston, Massachusetts 02115, United States)
Dijk, D. J.
Klerman, E. B.
Czeisler, C. A.
Date Acquired
August 22, 2013
Publication Date
November 1, 1998
Publication Information
Publication: The American journal of physiology
Volume: 275
Issue: 5 Pt 2
ISSN: 0002-9513
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: R01 MH-45130
CONTRACT_GRANT: P01 AG-09975
CONTRACT_GRANT: R01 AG-06072
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Regulatory Physiology
Non-NASA Center