State-trait arousal and daytime sleepiness after sleep restriction.

The importance of an arousal system in the regulation of sleepiness has been widely recognised in contexts of insomnia theory and research. Arousal is also incorporated in some general models of sleepiness and is considered one of the principal factors regulating sleepiness in a model by De Valck and Cluydts (2003), in which arousal has both state and trait components. In the present experimental study, we explored the effects of state and trait components of arousal on subjective sleepiness and sleep latency during daytime. On a day after partial sleep deprivation, 28 good sleepers aged 18-26 years took part in two successive experimental conditions, in which the state arousal was manipulated by laboratory tasks. We measured physiological (heart rate, frequency of skin conductance responses) and subjective (Energy, Tension, Anxiety) indices of state arousal, while trait arousal was operationalised as electrodermal lability. After a moderately stressful task, which induced a relatively higher state arousal, the participants reported lower sleepiness and took longer to fall asleep than after a simple psychomotor task. Trait arousal was not associated with daytime sleepiness. The results of this study support the idea that short-term changes of state arousal are important for the regulation of sleepiness in good sleepers, even in a situation which is only moderately stressful.