Sleep patterns and sleep disorders among female shift workers in a computer factory of Japan

Using a repeated questionnaire survey for female workers in a computer factory of Japan, consisting of 45 daytime workers and 84 weekly rotating shift workers (of whom 40 and 44 were respectively engaged in early-shift work and late-shift work during the survey week), the present study aimed to clarify the effects of shift work on their sleep patterns and sleep disorders. The time of retiring, time of rising, duration of sleep, and self-evaluated sleep quality based on four sleep-related problems were investigated for four days (Sunday-Monday, Tuesday-Wednesday, Thursday-Friday, and Saturday-Sunday) in a week. The intergroup comparison revealed that the earlier the rising time and the shorter the duration of sleep, the lower the sleep quality; the lowest sleep quality was observed in the early-shift workers.