Circadian and homeostatic modulation of sleep in older adults during a 90-minute day study.
OBJECTIVE
To identify age-associated changes in circadian and homeostatic characteristics of sleep in healthy elderly and young adults using electroencephalogram (EEG) power spectral analysis during a 90-minute sleep-wake schedule.


METHODS
Controlled clinical experiment.


METHODS
University sleep laboratory.


METHODS
16 older (77 +/- 5 years) and 19 younger adults (23 +/- 3 years).


METHODS
Subjects followed a 90-minute sleep-wake schedule (30 minutes in bed, 60 minutes awake) for 60 hours. Sleep was recorded for each bed-rest episode, and core body temperature was continuously recorded. The EEG power density was determined for non-rapid eye movement sleep in each bed-rest episode. Power density data were analyzed with mixed-effects models to assess rhythmic and linear components.


RESULTS
Younger subjects had greater power in delta, theta, and sigma power bands across the study interval. Significant circadian rhythms were observed in delta, sigma, and beta power bands. Age-related differences in circadian modulation of EEG activity, indicated by significant interaction terms, were present in alpha and beta bands. A significant linear component was present in delta and theta power bands, with no significant age-interaction effect.


CONCLUSIONS
Despite overall differences in the level of EEG power, older and younger adults exhibited similar rhythmic and linear patterns in most frequency bands. Age appears to affect circadian rhythmicity in higher EEG frequencies and homeostatic drive in lower EEG frequencies.
Niggemyer
Keith A
KA
Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh, Pennsylvania, USA.
Begley
Amy
A
Monk
Timothy
T
Buysse
Daniel J
DJ
D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology; D001510:Bed Rest; D001831:Body Temperature / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology