Objectives: To investigate whether work-time influence moderated the effect of shift work on psychological well-being measured as vitality, mental health, somatic stress symptoms, and disturbed sleep.
Methods: We used questionnaire data from 2,148 health care workers who finished their education in 2004 and were followed during their first 2 years of employment in the eldercare and health care sectors. We analyzed the effect of shift work, work-time influence, and the combination of these two variables adjusted for differences in baseline psychological well-being, background factors, and psychosocial work environment.
Results: Surprisingly, in this cohort, shift workers had higher vitality and better mental health than day workers. The combination of shift work and moderate or low work-time influence was associated with lower vitality, worse mental health, and more somatic stress symptoms than would have been expected when adding the separate effects of working hours and work-time influence. Work-time influence did not have any effect among day workers.
Conclusion: Shift workers appear to be especially vulnerable to the negative effect of moderate or low work-time influence.