Comparison of sleep quality based on direction of shift rotation in electronics workers.
BACKGROUND
Previous studies have reported the effects of direction of shift rotation on sleep, however, the findings are inconsistent. In this study, we investigated sleep quality related to direction of shift rotation using large-scale data from shiftwork-specific health examinations of electronics workers.


METHODS
This study included 4750 electronics workers working in a rotating 3-shift system who completed a medical examination for shift workers survey from January 1 to December 31, 2014, at a general hospital. The subjects were categorized into one of two groups according to direction of shift rotation. We compared sleep quality index between the subjects who worked in forward rotation and backward rotation systems.


RESULTS
Backward rotation was positively associated with prevalence of poor sleep quality. In the multivariable-adjusted model, when comparing backward rotation to forward rotation, the odds ratio (OR) with 95 % confidence interval (95 % CI) for poor sleep quality was 1.95 (1.58-2.41). After stratifying by gender, the ORs (95 % CIs) for poor sleep quality in male and female was 1.92 (1.47-2.49) and 2.13 (1.47-3.08), respectively. In subgroup analyses, backward rotation was significantly associated with poor sleep quality in workers ≥30 years of age compared with workers <30 years of age (adjusted OR 2.60 vs. 1.89, respectively; P for interaction <0.001).


CONCLUSIONS
Our study supports that a backward rotation system is associated with poor sleep quality. Forward rotation systems should be considered to reduce sleep problems.
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Youil
Y
Shon
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea ; Center for Cohort Studies, Total Healthcare Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea ; Department of Clinical Research Design & Evaluation, SAIHST, Sungkyunkwan University, Seoul, Korea.
Seungho
0000-0002-3927-8646
S
Ryu
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Byung-Seong
BS
Suh
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Soo-Geun
SG
Kim
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Won-Sool
WS
Kim
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Hee-Seung
HS
Son
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Hee-Yun
HY
Kim
Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
Han-Seur
HS
Jeong
Electronics workers; Shift rotation; Shiftwork; Sleep quality