Relationship between insomnia and rest time between shifts among shift workers: A multicenter cross-sectional study

Objectives: A rest time of less than 11 h taken by a shift worker between shifts is defined as quick return (QR). QR is shown to decrease sleep time by virtue of decreasing rest time, diminishing sleepiness and exhaustion, and increasing the number of sick days taken by employees. Therefore, in this multicenter retrospective study, the association between QR and the incidence of insomnia was established using the night-shift questionnaire from the Korean Workers Health Examination-Common Data Model. Methods: Three hospitals collected the night-shift profiles and baseline demographic data of 33 669 workers between January 2015 and December 2017. The most recent date of examination was used for participants who had been examined multiple times at the same institution. We used multiple logistic regression to calculate the odds ratios (ORs) and 95% confidence intervals (CIs). The pooled ORs were estimated using combined results from the three institutions. Results: The proportion of men was higher than that of women in the QR group at each institution. The pooled ORs were computed using combined data from the three institutions. Workers who reported a QR had the highest risk of sleeplessness (OR, 1.21; 95% CI, 1.12–1.31) compared to those workers who reported a slow return, after adjusting for possible confounders. Conclusions: A substantial correlation was established between QR and insomnia using the CDM approach and data from multiple centers. This study may serve as a foundation for developing guidelines to enhance the health of shift workers and prevent occupational accidents.