Fatigue among Employees Who Work Over the Karoshi Line (More Than 80 Hours Overtime per Month): Hybrid Approach Based on Experimental and Field Studies

Introduction: Empirical data regarding the adverse effects of overtime have been gathered. However, little is known about the magnitude of overtime risk, although the existence of risk has been discussed. Notably, it is informative to understand the risk magnitude in specific situations in terms of prevention. This study was intended to illustrate the risk magnitude by comparing a 40-hour sleep deprivation experimental study and field study targeted at employees with long working hours.