EEG and subjective sleepiness during extended wakefulness in seasonal affective disorder: circadian and homeostatic influences.
BACKGROUND
Seasonal affective disorder (SAD) may reflect a disturbance of circadian phase relationships or a disturbance of sleep-wake dependent processes, both of which change daytime energy and sleepiness levels.


METHODS
Under the unmasking conditions of a 40-hour constant routine protocol (CR), self-rated sleepiness and waking electroencephalogram (EEG) power density were assessed in women with SAD (n = 8) and in age-matched healthy control subjects (n = 9).


RESULTS
There was no significant effect of season or light treatment in any of the measures. The time course of subjective sleepiness was characterized by a circadian modulation and an overall increase during extended wakefulness in both SAD patients and control subjects. A prominent circadian rhythm of subjective sleepiness was not different in SAD patients and control subjects; however, the progressive buildup of sleepiness, as quantified by nonlinear regression analysis, was significantly reduced in SAD patients, mainly because they were sleepier than control subjects during the first 12 hours of the CR. The time course of waking EEG theta-alpha activity showed a more rapid increase during the first 10 hours of the CR in SAD patients. In contrast to control subjects who showed a progressive increase in the course of the 40-hour episode of extended wakefulness, EEG theta-alpha activity in SAD patients did not further increase over the remainder of the CR.


CONCLUSIONS
The data suggest that SAD patients may have a trait (rather than state) deficiency in the homeostatic buildup of sleep pressure during extended wakefulness as indexed by subjective sleepiness and EEG theta-alpha activity.
Cajochen
C
C
Chronobiology and Sleep Laboratory, Psychiatric University Clinic, University of Basel, Basel, Switzerland.
Brunner
D P
DP
Kräuchi
K
K
Graw
P
P
Wirz-Justice
A
A
D000328:Adult; D000368:Aged; D000513:Alpha Rhythm / Q000523:psychology; D015415:Biomarkers; D016022:Case-Control Studies; D002940:Circadian Rhythm; D003866:Depressive Disorder / Q000150:complications / Q000235:genetics / Q000503:physiopathology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008875:Middle Aged; D016574:Seasonal Affective Disorder / Q000150:complications / Q000235:genetics / Q000503:physiopathology*; D012892:Sleep Deprivation / Q000503:physiopathology* / Q000523:psychology*; D012894:Sleep Stages; D013826:Theta Rhythm / Q000523:psychology
D015415:Biomarkers