Work, Nonwork, and Sleep: The Role of Individual Factors and the Social Work Environment

Employees' sleep often receives too little attention compared to issues such as exercise and nutrition. However, sleep problems among employees are widespread and have even increased in recent years (Kronholm et al., 2016). This information is worrying as restful sleep has a crucial impact on the health, performance and occupational safety of employees (Brossoit et al., 2019; Litwiller et al., 2017). Healthy sleep is therefore of great interest not only to employees, but also to organisations. The overall aim of this dissertation is to analyse the antecedents of employees' sleep quality and the explanatory mechanisms for promoting sleep quality. So far, it is not well understood why job demands, such as time pressure or a high workload, are important antecedents of reduced sleep quality as a long-term consequence (e.g., Van Laethem et al., 2018) and why they are not necessarily related to sleep impairments in the same night (e.g., Eggli et al., 2022). Therefore, based on the Stressor-Detachment Model (SDM; Sonnentag & Fritz, 2015), the present dissertation investigates whether detachment, the mental disconnection from work, mediates the (possible) relationship between job demands and sleep quality in the short and long term (Research Question 1). Furthermore, little is known to date about the role of employees' individual factors and the social work environment in the relationship between work, nonwork, and sleep (Crain et al., 2018). However, this knowledge is not only important for a better theoretical understanding, but also enables the derivation of tailored interventions to improve the employees' sleep quality. Therefore, following the work, nonwork, and sleep framework model of Crain et al. (2018), this dissertation investigates which individual factors of employees are relevant for their sleep quality (research question 2) and what role the social work environment plays for their sleep quality (research question 3). These three research questions are addressed in four manuscripts, which form the basis of this dissertation. In Manuscript 1, we examined whether employees who perceive social support from supervisors and colleagues are more likely to detach from work during nonwork and thus sleep better in the long-term during periods of high job demands. Taking into account individual factors such as type of employment (full- and part-time) and supervisor status (with or without) that might influence the associations between work, nonwork, and sleep, we also examined these relationships within subgroups of employees. A total of N = 1856 employees participated in a two-wave panel study providing representative data for the German adult population. Results showed that job demands predicted changes in sleep quality over a six-month period and that detachment fully mediated this effect. In addition, perceived social support buffered the indirect effect of job demands on sleep quality via detachment. Subgroup analyses indicated that these effects were particularly relevant for full-time employees and supervisors. Manuscript 2 examined detachment as a mediator of the relationship between job demands and sleep quality as a short-term outcome. In addition, we investigated whether differences in the generation of daily job demands and detachment explain why socially prescribed perfectionism (SPP; the belief that others expect perfection from oneself and fear of being criticised; Hewitt & Flett, 1991) compared to self-oriented perfectionism (SOP; exceptionally high demands on oneself; Hewitt & Flett, 1991) is associated with poorer sleep quality (e.g., Stricker et al., 2022). A total of N = 70 employees participated in a diary study that spanned a period of five consecutive days (day level N = 233). Results highlighted that detachment fully mediated the relationship between daily job demands and sleep quality the following night. Moreover, the results indicated that increased job demands and associated lack of detachment explain why SPP is associated with decreased sleep quality. The hypothesised opposite serial mediation for SOP was not confirmed, but these perfectionists were found to sleep better. In Manuscript 3, we investigated whether a brief and low-dose app-based mindfulness intervention during the workday could be an approach to simultaneously reduce perfectionistic concern cognitions (PCC; thoughts about failure, mistakes, and possible negative consequences; Molnar et al., 2020) and related procrastination (Prestele et al., 2020) and improve detachment and sleep quality. The intervention, consisting of 10 sessions of 9-15 minutes each, was evaluated using a randomised controlled design with pre-, post- and follow-up measurements at two-week intervals each. Sustained increases in mindfulness and sustained reductions in PCC were observed in the intervention group (n = 94) compared with the wait-list control group (n = 87). There were also continuous sustained reductions in procrastination and a short-term improvement in sleep quality. However, no intervention effect was found for detachment. Manuscript 4 examined the role of leaders' strain symptoms on their employees' sleep quality. Specifically, we tested whether leaders' rumination during nonwork time was associated with employees' sleep quality and whether this association could be explained by a serial process of leaders' health, resource-oriented leadership, and team members' rumination. A total of N = 94 leaders and N = 332 of their employees participated in a three-wave study with time intervals of 14 and 8 months. The results indicated that a serial process can be assumed between leaders' rumination and their employees' sleep quality through leaders' health, resource-oriented leadership, and team members' rumination. In summary, the manuscripts presented in this dissertation provide insight into the relationship between the three life domains of work, nonwork, and sleep, and highlight the role of individual factors and the social work environment on employees' sleep quality. Consistent with the SDM, our findings provide preliminary evidence that detachment mediates the relationship between job demands and sleep quality in the short and long-term. Our results also suggest that the associations between work, nonwork, and sleep are particularly relevant for full-time employees, supervisors, and socially prescribed perfectionists. In turn, mindfulness is an important resource that can reduce PCC and improve sleep quality. The reduction of strain symptoms in leaders and resource-oriented leadership behaviour, as well as perceived social support from supervisors and colleagues, offer further approaches to reducing strain symptoms in employees and thus promoting employees' sleep quality. This knowledge can be used to expand and optimise interventions to improve employees' sleep quality.