Relationship Between Delirium and Dementia

Dementia, including Alzheimer's disease, is one of the most devastating conditions of older age. Currently affecting nearly 7 million individuals in the U.S. and 24 million worldwide, dementia leads to total loss of memory and the ability to function independently - making it one of people's greatest fears of aging.

Delirium is an acute confusional state, a common and serious complication in older individuals that often follows surgery or serious illness. Sometimes accompanied by disorientation, paranoia and hallucinations, delirium develops in 14 to 56 percent of all hospitalized seniors, complicating hospital stays for over 2.5 million older individuals in the U.S. each year.

For the most part, dementia and delirium have been viewed as separate and distinct conditions. But a special section of The Journal of Gerontology: Medical Sciences, appearing in January 2007, looks at their interface, asking: Can delirium itself lead to the development of a cognitive disorder? Do delirium and dementia represent opposite ends of the same spectrum of disease, rather than two separate conditions?

"I have been studying delirium for 20 years," says Sharon Inouye, MD, MPH, a geriatrician at Beth Israel Deaconess Medical Center and Director of the Aging Brain Center at the Institute for Aging Research, Hebrew SeniorLife. "And the more cases I encounter, the more linkages I see with dementia. For a large proportion of older patients, the problem [of delirium] is never resolved. I routinely hear from patients' families, 'They went into the hospital, they became very confused, and they never recovered.'"

Inouye, a professor of medicine at Harvard Medical School, together with Luigi Ferrucci, MD, PhD, Chief of the Longitudinal Studies Section of the National Institute on Aging and Editor-in-Chief of the journal, which is published by the Gerontological Society of America, examined the relationship between these two widespread conditions during the "Aging Brain Center Scientific Symposium: The Interface of Delirium and Dementia," held last spring.

"Better understanding of delirium may represent a new window of opportunity for the prevention of dementia," explains Ferrucci. "We, therefore, decided to approach the subject from a multidisciplinary perspective, exploring delirium and dementia from a number of vantage points." Findings spawned from the symposium make up the five articles featured in the special issue of the journal, including:

Biomarkers. "There is currently no way of identifying delirium save for the observations of an astute clinician," notes Inouye. In this review article, BIDMC geriatrician Edward Marcantonio, MD, examines a number of promising biomarkers for delirium, including serum chemistries,genetic markers, serum anticholinergic activity, neurotransmitters, inflammatory markers and cortisol.

Role of neuroimaging. Physicist David Alsop, PhD, of BIDMC's Department of Radiology, describes major advances in neuroimaging - including advanced methods using magnetic resonance (MR) imaging, positron emission tomography (PET) and single photo emission computed tomography (SPECT) - which offer the possibility of using highly sensitive imaging techniques to detect changes in the brain following episodes of delirium and thereby investigate the mechanisms and networks involved in its onset and consequences.