The sleep quality of subway drivers who work in the dark underground with an rotating shift system is generally poor, which can degrade the quality of a worker's life. This study examined the relationship between the sleep quality of subway worker and shift work by comparing three shift systems (rotating shift system, a three day shift system, and no-shift system).

Questionnaires including The short form of the Korean Occupational Stress Scale (KOSS), Pittsburgh Sleep Questionnaire (PSQI), the worker's age, gender, job type, accident, near miss and shift system were given to a total of 1010 workers. The results of 759 qualified questionnaires (75.15 %) were analyzed using the SPSS (ver 12.0) program.

The highest level of job stress was found among those working a rotating shift system followed by three shift system and no-shift system. The mean sleep quality score in the rotating shift workers was 5.1 (SD+/-3.2), which was greater than the sleep symptom score (5). 34.8% of rotating shift workers suffered from sleep symptoms. The sleep quality score by shift-work was significantly different. High job demand, strong external locus control, the experience of a near miss or an accident in the workplace during previous year has an adverse affect on the sleep quality. The sleep quality improved in case of a change into a no-shift system or a strong internal locus control.

A rotating shift system is more harmful to the quality of sleep in subway workers than a 3 shift system or no-shift system. In addition, job stress, personality, near miss and the experience of an accident affect the sleep quality of subway workers.