 This will be the first large cohort study to define the epidemiology of and identify modifiable risk factors for long-term CI and functional deficits of ICU survivors. We will measure the independent contribution of risk factors such as delirium and exposure to sedative and analgesic medications to the incidence of long-term CI, controlling for established risk factors e.g., age, pre-existing CI, and apoE genotype. Defining the contributions of these risk factors will make it possible to develop preventive andor treatment strategies to reduce the incidence, severity andor duration of long-term CI and improve functional recovery of patients with acute critical illness. 