Journal
PSYCHONEUROENDOCRINOLOGY
Volume 35, Issue 3, Pages 460-468Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.psyneuen.2009.08.017
Keywords
Sleep; Cortisol awakening response; Delay; PSG; Self-report; Older adults
Categories
Funding
- NIA [AG20677]
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The cortisol awakening response (CAR) is a burst of cortisol in response to awakening from steep that is superimposed on the circadian rhythm of cortisol. Determination of the CAR is contingent on the timing of sample collection: a delay between waking and collection of the first sample may affect the rise of the CAR, and could explain equivocal findings reported in the literature. We evaluated the impact of a delay between wake time and collection of waking cortisol samples on the CAR. Two methods were used to identify wake time: polysomnography (PSG) and self-report (S-R). Participants (total n = 207, mean age 74.0 +/- 7.2 years) included bereaved older adults (n = 35), caregivers (n = 50), patients with insomnia and co-morbid medical disorders (n = 68), and the healthy older adults (n = 54). We used ANOVA to test if a delay > 15 min affected the CAR. We also fitted cubic spline models to assess expected cortisol levels, the expected CAR, and the expected decrease in CAR. Wake times measured by PSG and S-R did not differ significantly. Large delays were observed (for both PSG and S-R) between wake time and collection of the waking cortisol sample (24.8 +/- 32.2 min for PSG and 28.3 +/- 49.2 min for S-R). Both statistical methods indicated that a delay > 15 min between wake time and first cortisol sample collection significantly affected the CAR (p's < .005); later collection times were associated with smaller CAR values. Later collection times and reduced CAR values may affect the interpretation of clinical associations. Our data also show that S-R assessments of wake time perform equally well to PSG for evaluating adherence with CAR sampling procedures. (c) 2009 Elsevier Ltd. All rights reserved.
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