Sleep Has Many Faces: The Interplay of Sleep and Work in Predicting Employees' Energetic State Over the Course of the Day

Sleep affects employees' functioning. In this study, we differentiate biological (chronotype), quantitative (daily sleep duration), and qualitative (daily sleep quality) sleep characteristics and examine their relationship with the trajectory of employees' vigor over the course of the day. Building on the two-process model of sleep regulation and the job demands-resources model, we examine whether sleep characteristics are differentially related to the trajectory of vigor as an energetic state. Furthermore, we expect that favorable sleep characteristics have a protective function during the workday in the interplay with daily job demands (workload) and job resources (autonomy). We conducted an experience-sampling study across ten workdays with three daily measurement occasions (171 employees, 1,631 days, 4,351 measurement occasions). Multilevel growth curve modeling showed that, on average, vigor followed a positive quadratic daily trajectory, mainly characterized by a decrease in vigor over the course of the day-after a slight increase early in the day. The decrease in vigor was particularly strong after nights with high sleep quality and for employees with an early chronotype. However, the relation between sleep quality and decrease in vigor occurred only on days with high workload. These results emphasize the importance of looking at the differential effects of sleep characteristics and on-the-job experiences on employees' energetic state during the day. These findings provide helpful suggestions on how to structure work and leisure time.