The mediating effects of working hours, sleep duration, and depressive mood on the association between shift work and the risk of suicidal ideation in Korean workers

Objectives: This study aimed to investigate the mediating effects of working hours, sleep duration, and depressive mood on the association between shift work and the risk of suicidal ideation in Korean workers. Methods: Data from 33,047 workers were obtained from the nationwide cross-sectional Korea National Health and Nutrition Examination Surveys conducted in 2007–2018. Healthy workers without depressive disorders and chronic medical illnesses were included in the current study. Shift work patterns, sleep duration, working hours, depressive mood, and suicidal ideation were assessed using self-reported questionnaires. Multivariate logistic regressions were used to examine the association between shift work and the risk of suicidal ideation. Additionally, mediating studies were conducted to identify the roles of working hours and sleep durations on the association. Results: Compared with daytime workers, shift workers had 1.33 times greater risk of suicidal ideation (OR = 1.33, 95% Cl = 1.17–1.52, p < 0.001). Specifically, among shift work patterns, fixed-night shift, 24-h rotating shift and irregular rotating shift were associated with the risk of suicidal ideation when compared with daytime workers (irregular rotating shift: OR = 1.92, 95% Cl = 1.29–2.86, p = 0.001; fixed-night shift: OR = 1.75, 95% Cl = 1.32–2.31, p < 0.001; 24-h rotating shift: OR = 1.58, 95% Cl = 1.06–2.36, p = 0.024). In the mediating study, working hours, sleep duration and depressive mood significantly mediated the relationship between shift work and suicidal ideation (direct effect: β = 0.019, p = 0.001; indirect effect: β = 0.004, p = 0.031; total effect: β = 0.023, p < 0.001). Conclusion: This study revealed that shift workers had a greater risk of suicidal ideation. The patterns significantly associated with suicidal ideation were irregular rotating, fixed-night, and 24-h rotating shifts. The pathway analysis revealed serial mediating effects of working hours, sleep duration, and depressive mood on the association between shift work and suicidal ideation.