Daily sleep in relation to subjective and physiological stress in an occupational context: Daily vigour as a mediator.

Studies on the stress-sleep relationship consistently demonstrate negative effects of stress on sleep. The reversed relation, however, has received less research attention. Also, field studies on physiological stress are scarce. The aim of this day-level diary study was to examine daily relationships between sleep quality and quantity, and subjective and physiological stress in an occupational context. Moreover, we examined daily vigour as an underlying mechanism of the sleep-stress relationship. Participants were 167 knowledge workers who filled in daily questionnaires measuring sleep quality and quantity, morning vigour and subjective afternoon stress on Tuesdays and Thursdays for 5 weeks. Physiological stress was assessed with cortisol decline from morning peak to evening, and with blood pressure in the afternoon. Multilevel path analysis results showed that better sleep quality and longer sleep hours predicted increased vigour the following morning, which in turn predicted lower subjective stress in the afternoon. Sleep quality and quantity were not related to physiological stress neither directly nor indirectly via morning vigour. On the basis of our results, sleep should be considered as a factor affecting vigour which in turn seems to lower stress.