Background Delirium is defined as a disturbance in attention, awareness and cognition with reduced ability to direct, focus, sustain and shi attention, and reduced orientation to the environment. Critically ill patients in the intensive care unit (ICU) frequently develop ICU delirium. It can profoundly a ect both them and their families because it is associated with increased mortality, longer duration of mechanical ventilation, longer hospital and ICU stay and long-term cognitive impairment. It also results in increased costs for society. Objectives To assess existing evidence for the e ect of preventive interventions on ICU delirium, in-hospital mortality, the number of delirium-and coma-free days, ventilator-free days, length of stay in the ICU and cognitive impairment.