The epidemiology of delirium: a review of studies and methodological issues.

Information about the epidemiology of delirium has grown tremendously over the past 2 decades. However, methodological challenges have made this area of research difficult to study. Most studies have focused on the prevalence, risk factors, and course of delirium in elderly populations and acute medical and surgical settings. Growing evidence is showing that delirium is a neuropsychiatric syndrome that deserves more research and clinical attention. This article summarizes the current literature on the epidemiology of delirium and discusses some of the important methodological issues in conducting and interpreting research in this area.