Introduction: Elucidating the Pathophysiology of Delirium and the Interrelationship of Delirium and Dementia

DELIRIUM, defined as an acute decline of attention and cognitive function, represents a common and potentially devastating problem for hospitalized older persons. With occurrence rates from 14% to 56% and hospital mortality rates from 25% to 33% (1), delirium often initiates a cascade of events culminating in loss of independence, increased morbidity and mortality, and increased health care costs (2). We estimate, on the basis of our previous work (1,3) and extrapolations from Medicare data (4), that each year delirium complicates hospital stays for at least 20% of the 12.5 million persons aged 65 years and older who are hospitalized each year, with an increased hospital cost of $2,500 per patient attributable to delirium. This accounts for over $6.9 billion (2004 U.S. dollars) in Medicare expenditures for hospitalization attributable to delirium each year. Substantial additional direct health care costs accrue after hospital discharge because of the need for institutionalization, emergency room visits, rehospitalization, physician or clinic visits, rehabilitation services, and formal home health care, estimated at $48,785 per patient attributable to delirium, or over $100 billion per year extrapolated nationally (5).