"This study is important, as delirium is often overlooked and minimized in the hospital setting, especially in persons with dementia," said Donna M. Fick, Distinguished Professor of Nursing at Penn State and principal investigator for this study. "And it illustrates that delirium is deadly, costly and impacts patient functioning."

The researchers followed 139 hospitalized adults, ages 65 and older, with dementia and found that the patients who developed delirium had a 25 percent chance of dying within 30 days, as reported in the current issue of the Journal of Hospital Medicine.

Dementia is an irreversible, progressive condition that affects cognitive and physical function. Symptoms usually occur over months to years and can include memory loss, inability to solve simple problems, difficulties with language and thinking, personality and behavior changes and other mental problems.

Delirium, on the other hand, is a reversible cognitive condition that comes on quickly and if caught and treated early can be resolved. Many of the symptoms of delirium may appear similar to dementia, but signs such as marked inattention and sleepiness or hyperactivity can help differentiate delirium from dementia.

Fick and colleagues focused on this combination of disorders, known as delirium superimposed on dementia (DSD), in this study. The researchers found a 32 percent incidence of new delirium in the hospitalized patients with dementia. These patients stayed in the hospital about four days longer than patients without delirium, and also had a reduced level of physical and mental ability when they left the hospital and at follow-up visits one month later. Additionally, patients with DSD were more likely to have died a month after their hospital stay.

Previous studies have found the cost of delirious episodes rivals those for diabetes and heart disease. Decreasing the length of stay by just one day would save more than $20 million in health care costs per year.

Common causes of delirium are infections, dehydration and medication changes. A third of the patients in this study arrived at the hospital dehydrated.

"Preventing delirium is important because we want to discharge patients at their baseline or improved functioning," said Fick. "We do not want them to go home with worse functioning than when they came into the hospital."

The goal of the researchers is to help practitioners recognize and treat delirium in patients with DSD as early as possible, helping to improve quality of life for the patient.