Introduction: Irregular work schedules often results in a disruption of the normal circadian rhythm that can causes sleepiness when wakefulness is required and insomnia during the main sleep episode.
Method: Two physicians using the Sleep-EVAL system interviewed 817 staff members of a psychiatric hospital. The interviews were done during the working hours. In addition to a series of questions to evaluate sleep and mental disorders, the evaluation included a standard questionnaire assessing work conditions, work schedule and their consequences. Three work schedules were assessed: (1) fixed daytime schedule (n=442), (2) rotating daytime shifts (n=323) and (3) shift or nighttime work (n=52).
Results: Subjects working on rotating daytime shifts were younger than the two other groups and had a higher proportion of women. Participants working on rotating daytime shifts reported more frequently than the fixed daytime schedule workers to have difficulty initiating sleep (20.1% vs. 12.0%). The sleep duration of shift or nighttime workers was shorter than that of the two other groups. Furthermore, subjects working rotating daytime schedule reported to have shorter sleep duration of about 20 min when they are assigned to the morning shift. Work-related accidents were two times more frequent among the rotating daytime workers (19.5%) compared with the fixed daytime schedule workers (8.8%) and the group of nighttime or shift workers (9.6%). Sick leaves in the previous 12 months were also more frequently reported in the rotating daytime schedule group (62.8%) as compared with the daytime group (38.5%, P<.001); 51.9% of nighttime or shift workers took sick leave.
Conclusions: Working on a rotating daytime shifts causes significant sleep disturbances. As consequences, these workers are more likely to feel sleepy at work and are more likely to have work-related accidents and sick leaves.