Subjective Sleep Disturbances of Factory Workers in Relation to Shift Work Schedule and Chronotype

ABSTRACT

OBJECTIVES: Shift work in Korea is most prevalent in automobile system manufacturing industries. The subjective sleep complaints and individual chronotypes of shift worker was evaluated. METHODS: A cross-sectional study was conducted among single automobile system manufacturing industries in Korea. All participants completed questionnaires about the work schedule, duration of sustained employment and various division of work. And sleep questionnaires including Epworth Sleepiness Scale, Insomnia Severity Index, Hospital Anxiety and Depression Scale, and Morningness-Eveningness Questionnaire. RESULTS: This study enrolled 208 participants [shift workers (SWs)=142, day workers (DWs)=66]. Insomnia symptoms were significantly worse in the SW group (p<0.001). Excessive daytime sleepiness was not significantly different between groups. The evening chronotype in DWs was related to both excessive daytime sleepiness (EDS) (p=0.008) and insomnia (p=0.034). On the other hand, chronotypes in SWs were not significantly different in terms of EDS and insomnia. CONCLUSIONS: Insomnia symptoms were significant in SWs compare to DWs. In DWs the evening types were sleepier and had more insomnia symptoms than other chronotypes. The sleep symptoms are prevalent in automobile industries workers, and in part it is related to work schedule and individual chronotype.