Until the 5-year follow-up, 896 participants were observed, and 486 participants survived through the 10-year follow-up. At baseline, 1,500 gainfully employed subjects, 45–73 years of age and without a history of depression, were included. We performed various sensitivity and stratified analyses to test the robustness of our results. Poisson regression with robust error variances was calculated to estimate relative risks (RR) and 95% confidence intervals (CI), adjusted for age at follow-up, diurnal preference, monthly household income and education. The definition of shift work included work hours outside 7:00 to 18:00, whereas night work was defined as a shift including work between 0:00 and 5:00.

Depressive symptoms were assessed using the Center for Epidemiologic Studies-Depression (CES-D)-Scale (≥17 points defined as high symptoms) and the Patient Health Questionnaire (PHQ) with a cutoff ≥9, or prescription of an anti-depressant. We studied the association between shift work and depressive symptoms in the prospective Heinz Nixdorf Recall Study, considering various demographic, lifestyle and work-related factors. Shift workers appear to be especially vulnerable to the negative effect of moderate or low work-time influence.

Work-time influence did not have any effect among 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. Surprisingly, in this cohort, shift workers had higher vitality and better mental health than day workers. 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. 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. 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.

Extend worktime on lg env3