Delirium often develops in elderly patients during hospitalization or serious illness, and this acute state of confusion and agitation has long been suspected of having ties to Alzheimer's disease and other dementias.
Now a study led by researchers at Beth Israel Deaconess Medical Center (BIDMC) and Hebrew Senior Life confirms that an episode of delirium rapidly accelerates cognitive decline and memory loss in Alzheimer's patients. The findings are reported in the May 5 issue of the journal Neurology.
"The cognitive rate of decline was found to be three times more rapid among those Alzheimer's patients who had had an episode of delirium than among those who did not have such a setback," according to lead author Tamara Fong, MD, a staff neurologist at BIDMC and Assistant Scientist at the Institute for Aging Research, Hebrew Senior Life. "In other words, the amount of decline you might expect to see in an Alzheimer's patient over the course of 18 months would be accelerated to 12 months following an episode of delirium."
Alzheimer's disease is an irreversible, progress form of dementia that gradually destroys a person's ability to carry out even the simplest of tasks, and affects as many as 4.5 million individuals in the U.S. according to figures from the National Institute on Aging. There is currently no cure for Alzheimer's disease.
Delirium, on the other hand, is a potentially preventable condition, which often develops following a medical disturbance, surgery or infection and is estimated to affect between 14 percent and 56 percent of all hospitalized elderly patients.
The investigators performed a secondary analysis of data gathered from 408 patients examined between 1991 and 2006 at the Massachusetts Alzheimer's Disease Research Center (MADRC). Over this 15-year period, MADRC staff conducted a number of memory tests on patients. Testing was done on at least three occasions, separated by intervals of approximately six months. Seventy-two of the participants developed delirium during the course of the study.
In their final analysis, the authors found that among patients who developed delirium, the average decline on cognitive tests was 2.5 points per year at the beginning of the study; following an episode of delirium, decline nearly doubled to 4.9 points per year.
"Although each dementia patient declines at his or her own individual rate, the results of our study tell us that this rate can increase three-fold following an episode of delirium," says Fong. "As an example, suppose an Alzheimer's patient begins with mild symptoms, such as forgetting appointments or details of conversations, but over a period of the next 18 months, loses the ability to identify relatives, becomes lost while driving familiar routes, or can no longer balance a checkbook or manage financial transactions. This same patient, were he or she to experience an episode of delirium, might experience this same rate of decline in only 12 months."