The circadian and homeostatic modulation of sleep pressure during wakefulness differs between morning and evening chronotypes

Core body temperature and subjective sleepiness occurred 1.5 hours and 2 hours later, respectively, in evening-type subjects compared to morning-type subjects.

• Morning-type subjects displayed a bimodal rhythm of sleep-wake propensity, while evening-type subjects did not.
• The buildup of subjective sleepiness was slower in evening-type than in morning-type subjects.
• EEG theta-alpha activity patterns followed an exponential curve for both chronotypes.
• The time constant for sleep pressure increase was longer in evening types, indicating a slower buildup of sleepiness.

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