Many hospitals have adopted a 12-hour work shift for nurses and some studies have shown a resulting increase in burnout and decrease in patient safety. In this study, researchers assessed simulated nursing performance, cognition, and sleepiness in day nurses and night nurses who worked three consecutive 12-hour shifts. Overall results indicated nurses on both shifts mostly maintain their abilities on the simulated nursing performance assessment despite reporting increased sleepiness and fatigue. However there was more individual variation in cognition and some domains of performance.