Insomnia Symptoms and Mood Disturbances in Shift Workers with Different Chronotypes and Working Schedules

Shift workers frequently suffer from insomnia and mood disturbances, but little is known about the relationships of these conditions with the chronotypes and different working schedules of shift workers. We hypothesized that different shift-work schedules are associated with different severities of sleep and mood disturbances, and that the individual chronotype plays a role in sleep disturbances in shift workers.

This study enrolled 276 participants, comprising 77 nurses working in a three-shift schedule (3S, 27.9%), 60 firefighters working in a 24-h-every-other-day shift schedule (EOD, 21.7%), and 139 day workers (DW, 50.4%). All of the participants completed the following questionnaires to assess their sleep disturbances, mood, and chronotype: Insomnia Severity Index (ISI), Epworth Sleepiness Scale, Hospital Anxiety and Depression Scale, and Morningness-Eveningness Questionnaire.

ISI questionnaires were worse in both shift workers compare to DW, 35.1% of 3S, 23% of EOD had clinically significant insomnia (ISI score >14). Depressive mood and anxiety symptom were significantly worse in 3S compare to EOD. The sleep disturbance by ISI score had significant correlations with depressive mood and anxiety symptoms for both EOD and 3S (EOD: rho=0.57, rho=0.57, 3S: rho=0.37, rho=0.33 respectively). Chronotype type in shift workers had no significant correlation with sleep disturbance, depressive mood, nor anxiety symptom. However, after adjustment, the eveningness chronotype have relationship to the depressive mood in shift workers.

Sleep disturbances are more frequent in shift workers than DW. Depressive mood and anxiety symptoms were frequently reported in 3S, then EOD. Different shift schedules cab be a determinant of depressive mood and anxiety symptom.