Lifestyle Factors in the Association of Shift Work and Depression and Anxiety

IMPORTANCE Shift work may lead to adverse health outcomes. Whether shift work is associated with depression and anxiety, and to what extent lifestyle mediates the associations, remains unknown. OBJECTIVE To explore the associations of shift work, its type, frequency, and working years with anxiety and depression and to examine the potential mediating role of lifestyles. Design, Setting, and Participants This cohort study included 175 543 employed or self-employed workers who participated in the UK Biobank baseline survey (2006-2010). Data analysis was conducted from November 2022 to January 2023. EXPOSURES Employment and shift work status information was obtained from baseline. Lifestyles included smoking, physical activity, alcohol consumption, dietary characteristics, sleep duration, sedentary time, and body mass index (BMI). MAIN OUTCOMES AND MEASURES Depression and anxiety were identified based on electronic health records. Cox proportional hazard regression models were used to calculate the association of shift work with anxiety and depression, and cause mediation analyses we used to test the mediating role of lifestyle factors in this association. RESULTS Of the 175 543 included participants (mean [SD] age, 52.6 [7.1] years; 88 290 men [50.3%]; 167 495 White participants [95.4%]), 27 637 participants (16.2%) reported shift work. During a median (IQR) follow-up of 9.06 (8.35-9.75) years, 3956 workers (2.3%) developed depression and 2838 (1.7%) developed anxiety. In the fully adjusted model, individuals who reported engaging in shift work, or shift workers, had a higher risk of depression (HR, 1.22; 95% CI, 1.12-1.33; P < .001) and anxiety (HR, 1.16; 95% CI, 1.04-1.28; P < .001), and the risk was positively associated with shift frequency. Among shift workers, there was no significant difference between night shifts and nonnight shifts. In the dose-association analyses, years of shift work were negatively associated with the risk of depression and anxiety. Smoking, sedentary time, BMI, and sleep duration were identified as the main potentially modifiable mediators. These mediators together explained 31.3% of the association between shift work and depression and 21.2% of the association between shift work and anxiety. CONCLUSIONS AND RELEVANCE In this cohort study, shift work was significantly associated with a higher risk of depression and anxiety, and lifestyle factors partially mediated the associations. These findings not only support that shift work should be considered an occupational hazard, but also provide evidence for the urgent need for the development of public health interventions that promote healthy lifestyles aimed at improving the mental health of shift workers.