Fatigue and somatization in shift-workers: Effects of depression and sleep

Objective: We investigated the differences in fatigue and somatization between shift and non-shift workers and explored the effects of sleep and depression on fatigue and somatization in shift workers. Methods: In total, 4543 shift workers and 2089 non-shift workers completed self-reported questionnaires. The Center for Epidemiologic Studies Depression Scale (CES[sbnd]D), Pittsburgh Sleep Quality Index (PSQI), Fatigue Severity Scale (FSS), and Somatization subscale of the Symptom Checklist 90-item version (SCL-SOM) were used to measure depression, sleep quality, fatigue, and somatization, respectively. Fatigue and somatization were compared between shift and non-shift workers after controlling for different sets of covariates. Results: Compared to non-shift workers, shift workers reported higher FSS (mean difference: 2.19 ± 0.30, p < 0.01) and SCL-SOM (mean difference: 1.77 ± 0.21, p < 0.01) scores after controlling for age, gender, presence of medical illness, occupational category, monthly income, length of service, and weekly working hours. The between-group difference in FSS score was no longer significant after additionally controlling for CES-D (p = 0.15) or PSQI (p = 0.18). The between-group difference in SCL-SOM score showed only non-significant trends after additionally controlling for CES-D (p = 0.09) or PSQI (p = 0.07). The group difference in SCL-SOM scores disappeared after controlling for both CES-D and PSQI scores (p = 0.99). Conclusions: Shift workers had higher fatigue and somatization levels than non-shift workers and the group difference was associated with disturbed sleep and depressed mood in shift workers.