The natural history of delirium in older hospitalized patients: a syndrome of heterogeneity.

OBJECTIVES To determine the presentation, course and duration of delirium in hospitalized older people. DESIGN Observational cohort study. SETTING Inpatient surgical and medical wards at a university hospital. PARTICIPANTS 432 people over the age of 65. MEASUREMENTS All participants were screened daily for confusion and, in those who were confused, delirium was ascertained using the Diagnostic and Statistical Manual of Mental Disorders (DSM) III-R criteria. Those who were found to be delirious were followed daily while in hospital for evidence of delirium. The Delirium Rating Scale (DRS) was used to describe the clinical characteristics of delirium. RESULTS About 15% of subjects had delirium. Sixty-nine percent of delirious subjects had delirium on a single day. The DRS total was higher on the first day of delirium for those with delirium on multiple days than those with delirium on a single day (P = 0.03). Among those with delirium on multiple days, there were no patterns of change over time in specific DRS items. CONCLUSIONS Delirium in hospitalized older people is common and has a varied presentation and time course. Clinicians and researchers need to consider this great heterogeneity when caring for patients and when studying delirium.