Circadian and wake-dependent influences on subjective sleepiness, cognitive throughput, and reaction time performance in older and young adults.
OBJECTIVE
To assess circadian and homeostatic influences on subjective sleepiness and cognitive performance in older adults when sleep and waking are scheduled at different times of day; to assess changes in subjective sleepiness and cognitive performance across several weeks of an inpatient study; and to compare these findings with results from younger adults.


METHODS
Three 24-h baseline days consisting of 16 h of wakefulness and an 8-h sleep opportunity followed by 3-beat cycles of a 20-h forced desynchrony (FD) condition; 18 20-h "days," each consisting of 13.33 h of scheduled wakefulness and 6.67 h of scheduled sleep opportunity.


METHODS
Intensive Physiological Monitoring Unit of the Brigham and Women's Hospital General Clinical Research Center.


METHODS
10 healthy older adults (age 64.00 +/- 5.98 y, 5 females) and 10 healthy younger adults (age 24.50 +/- 3.54 y, 5 females).


METHODS
Wake episodes during FD scheduled to begin 4 h earlier each day allowing for data collection at a full range of circadian phases.


RESULTS
Subjective sleepiness, cognitive throughput, and psychomotor vigilance assessed every 2 h throughout the study. Core body temperature (CBT) data collected throughout to assess circadian phase. Older subjects were less sleepy and performed significantly better on reaction time (RT) measures than younger subjects. Decrements among younger subjects increased in magnitude further into the experiment, while the performance of older subjects remained stable.


CONCLUSIONS
Our findings demonstrate that the waking performance and alertness of healthy older subjects are less impacted by the cumulative effects of repeated exposure to adverse circadian phase than that of young adults. This suggests that there are age-related changes in the circadian promotion of alertness, in the wake-dependent decline of alertness, and/or in how these 2 regulatory systems interact in healthy aging.
Silva
Edward J
EJ
Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA. esilva@rics.bwh.harvard.edu
Wang
Wei
W
Ronda
Joseph M
JM
Wyatt
James K
JK
Duffy
Jeanne F
JF
D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D001143:Arousal; D001831:Body Temperature; D002940:Circadian Rhythm; D003071:Cognition; D003072:Cognition Disorders / Q000150:complications* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011597:Psychomotor Performance; D011930:Reaction Time; D020178:Sleep Disorders, Circadian Rhythm / Q000150:complications / Q000503:physiopathology; D012893:Sleep Wake Disorders / Q000150:complications* / Q000503:physiopathology; D014851:Wakefulness; D055815:Young Adult
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