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 assess whether sleep quality was a mediating factor.

Design: Cross-sectional study.

Setting: 11 manufacturing factories in Malaysia.

Participants: 177 night-shift workers aged 40 to 65 years old were compared with 317 non-night-shift work.

Primary and secondary outcomes: Participants completed a self-administered questionnaire on socio-demography and lifestyle factors, short Form-12v2 Health Survey (SF-12), and the Pittsburgh Sleep Quality Index (PSQI). Baron and Kenny’s method, Sobel test and multiple mediation model with bootstrapping were used 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 to 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, standard error [SE]=0.14, bias corrected 95%Confidence Interval [BC 95%CI]: -0.58 to -0.01) and “sleep disturbances” (indirect effect=-0.79, SE=0.22, BC 95%CI: -1.30 to -0.42) were mediators for the association between night-shift work and physical wellbeing, whereas “sleep latency” (indirect effect=-0.51, SE=0.21, BC 95%CI: -1.02 to -0.16) and “daytime dysfunction” (indirect effect=-1.11, SE=0.32, BC 95%CI: -1.86 to -0.58) were mediators with respect to mental wellbeing.

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 in order to improve their employees’ overall wellbeing.

Data was collected from participants of SOCSO HSP.

The demographic and lifestyle characteristics of participants were compared according to their shift work status. All categorical variables were described by proportions and compared using Chi-square test. The non-parametric Mann-Whitney U test was used for asymmetrical continuous variables.

The Baron and Kenny’s method and Sobel test were applied to assess whether the association between night-shift work and HRQoL was mediated by the PSQI global score.

To explore sleep quality dimensions, multiple mediation analysis using the PROCESS macro on SPSS version 21 developed by Hayes was employed to test a multiple mediation model with the seven components of the PSQI

Readme

1. Data include raw data 

2. Analysis using bootstrapping method to determine whether sleep mediate shift work and QOL

3. Baron and Kenny method to determine lifestyle factor mediate shift work and QOL