An endogenous circadian rhythm in sleep inertia results in greatest cognitive impairment upon awakening during the biological night

Frank A. J. L. Scheer, Thomas J. Shea, Michael Hilton and Steven A. Shea (2008) An endogenous circadian rhythm in sleep inertia results in greatest cognitive impairment upon awakening during the biological night. Journal of Biological Rhythms, 23 4: 353-361. doi:10.1177/0748730408318081


Author Frank A. J. L. Scheer
Thomas J. Shea
Michael Hilton
Steven A. Shea
Title An endogenous circadian rhythm in sleep inertia results in greatest cognitive impairment upon awakening during the biological night
Journal name Journal of Biological Rhythms   Check publisher's open access policy
ISSN 0748-7304
Publication date 2008-08
Sub-type Article (original research)
DOI 10.1177/0748730408318081
Volume 23
Issue 4
Start page 353
End page 361
Total pages 9
Editor Martin Zatz
Place of publication New York, U.S.A.
Publisher Sage Science Press
Collection year 2009
Language eng
Subject 321204 Mental Health
C1
920209 Mental Health Services
111714 Mental Health
0606 Physiology
1116 Medical Physiology
Abstract Sleep inertia is the impaired cognitive performance immediately upon awakening, which decays over tens of minutes. This phenomenon has relevance to people who need to make important decisions soon after awakening, such as on-call emergency workers. Such awakenings can occur at varied times of day or night, so the objective of the study was to determine whether or not the magnitude of sleep inertia varies according to the phase of the endogenous circadian cycle. Twelve adults (mean, 24 years; 7 men) with no medical disorders other than mild asthma were studied. Following 2 baseline days and nights, subjects underwent a forced desynchrony protocol composed of seven 28-h sleep/wake cycles, while maintaining a sleep/wakefulness ratio of 1:2 throughout. Subjects were awakened by a standardized auditory stimulus 3 times each sleep period for sleep inertia assessments. The magnitude of sleep inertia was quantified as the change in cognitive performance (number of correct additions in a 2-min serial addition test) across the first 20 min of wakefulness. Circadian phase was estimated from core body temperature (fitted temperature minimum assigned 0°). Data were segregated according to: (1) circadian phase (60° bins); (2) sleep stage; and (3) 3rd of the night after which awakenings occurred (i.e., tertiary 1, 2, or 3). To control for any effect of sleep stage, the circadian rhythm of sleep inertia was initially assessed following awakenings from Stage 2 (62% of awakening occurred from this stage; n = 110). This revealed a significant circadian rhythm in the sleep inertia of cognitive performance (p = 0.007), which was 3.6 times larger during the biological night (circadian bin 300°, ~2300–0300 h in these subjects) than during the biological day (bin 180°, ~1500–1900 h). The circadian rhythm in sleep inertia was still present when awakenings from all sleep stages were included (p = 0.004), and this rhythm could not be explained by changes in underlying sleep drive prior to awakening (changes in sleep efficiency across circadian phase or across the tertiaries), or by the proportion of the varied sleep stages prior to awakenings. This robust endogenous circadian rhythm in sleep inertia may have important implications for people who need to be alert soon after awakening.
Keyword Circadian rhythm
Cognitive performance
Grogginess
Jet lag
Sleep inertia
Sleep
Q-Index Code C1
Q-Index Status Confirmed Code

 
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