[Mediated effect of sleep disorders on the association between shift work and major depressive symptoms]

Objective: To explore the association between shift work and major depressive symptoms and assess the mediating role of sleep disorders based on observation study and Mendelian randomization (MR) analysis. Methods: A convenience sampling method was adopted to conduct a survey on 1087 workers in a petrochemical enterprise in a city of Henan Province in April 2022. A total of 857 research subjects were included in the subsequent analysis after excluding the angualified research subjects. Logistic regression analysis was used to investigate the association between shift work and major depressive symptoms, and mediation analysis was used to evaluate the mediating role of sleep disorders. The GWAS summary data for MR analysis were obtained from the IEU Open GWAS project database. Inverse variance weighted method was used as the main analysis of MR analysis, and the mediating effect of insomnia and sleep duration between shift work and major depressive symptoms was assessed by two-step MR analysis. Results: In the adjusted model, participants with shift work had a higher risk for major depressive symptoms[OR (95%CI) : 1.91 (1.34-2.73), P<0.01], and a higher sleep disorder score[β (95%CI) : 1.36 (0.34-2.37), P<0.01] than those without shift work. Additionally, sleep disorder score was positively associated with major depressive symptoms[OR (95%CI) : 1.29 (1.24-1.35), P<0.01]. Mediated analysis showed that sleep disorders partially mediated the association between shift work and major depressive symptoms, accounting for 43.32% (95%CI) : 10.43%-77.01%. Mendelian randomization analysis showed a significant causality between shift work and major depressive symptoms [OR= (95%CI) : 1.23 (1.13-1.33), P<0.01], and the mediated proportion of insomnia and sleep duration was 13.53% (1.93%-26.37%) : and 7.25% (0.48%-15.94%), respectively. Conclusion: Sleep is an important mediating factor between shift work and major depressive symptoms, which indicated that improving sleep status of individuals with shift work may be an effective measure to reduce the incidence of depressive symptoms.