Objectives Night-shift work may adversely affect health. This study aimed to determine the impact of night-shift work on health-related quality of life (HRQoL), and to assess whether sleep quality was a mediating factor.
Design A cross-sectional study.
Setting 11 manufacturing factories in Malaysia.
Participants 177 night-shift workers aged 40–65 years old were compared with 317 non-night-shift workers.
Primary and secondary outcomes Participants completed a self-administered questionnaire on socio-demographics and lifestyle factors, 12-item Short Form Health Survey V.2 (SF-12v2) and the Pittsburgh Sleep Quality Index (PSQI). The Baron and Kenny’s method, Sobel test and multiple mediation model with bootstrapping were applied to determine whether PSQI score or its components mediated the association between night-shift work and HRQoL.
Results Night-shift work was associated with sleep impairment and HRQoL. Night-shift workers had significantly lower mean scores in all the eight SF-12 domains (p<0.001). Compared with non-night-shift workers, night-shift workers were significantly more likely to report poorer sleep quality, longer sleep latency, shorter sleep duration, sleep disturbances and daytime dysfunction (p<0.001). Mediation analyses showed that PSQI global score mediated the association between night-shift work and HRQoL. ‘Subjective sleep quality’ (indirect effect=−0.24, SE=0.14 and bias corrected (BC) 95% CI −0.58 to −0.01) and ‘sleep disturbances’ (indirect effect=−0.79, SE=0.22 and BC 95% CI −1.30 to −0.42) were mediators for the association between night-shift work and physical well-being, whereas ‘sleep latency’ (indirect effect=−0.51, SE=0.21 and BC 95% CI −1.02 to −0.16) and ‘daytime dysfunction’ (indirect effect=−1.11, SE=0.32 and BC 95% CI −1.86 to −0.58) were mediators with respect to mental well-being.
Conclusion Sleep quality partially explains the association between night-shift work and poorer HRQoL. Organisations should treat the sleep quality of night-shift workers as a top priority area for action to improve their employees’ overall wellbeing.
- shift work
- quality of life
- sleep quality
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Contributors The study conception was by YCL and NB-P. YCL, VH and NB-P designed the study, conducted the statistical analysis and interpreted the results. YCL and AD collected the data. YCL, VH, AD and NB-P drafted the manuscript. All authors have read and approved the final version of the submitted manuscript.
Funding This study was funded by the University Malaya Post-Graduate Research Fund (PG139-2015A). Funding for publication was from the National Institutes of Health, Ministry of Health, Malaysia.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Ethical approval was obtained from Medical Ethics Committee of University of Malaya Medical Centre (MECID.NO: 20 154–1234).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available in a public, open access repository. Data are available upon reasonable request. Extra data can be accessed via the Dryad data repository at http://datadryad.org/ with the doi: 10.5061/dryad.905qftthw.
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