Apprehension of the subsequent working day is associated with a low amount of slow wave sleep.

Stress is probably the most frequent cause of short-term insomnia, although it has seldom been documented polysomnographically. A few studies have shown that apprehension is associated with a reduction of slow wave sleep (SWS). The aim of the present study was to examine whether apprehension of the next working day would be related to sleep polysomnography and subjective sleep quality. In this analysis we made use of two different studies (n = 37, mean age: 37 years) that provided inter-individual variation in apprehension of the subsequent working day. The results confirm previous findings that apprehension of a difficult next day is associated with decreased amount of SWS, increased percentage of stage 2 sleep, bedtime state anxiety and subjectively poor sleep. It is concluded that moderate "everyday" stress may disturb physiological restoration as indicated by the reduction of SWS.