FRIDAY, Sept. 20 (HealthDay News) -- More than half of patients with dementia will experience delirium while hospitalized -- and failure to detect that delirium results in a quicker decline of these patients' physical and mental health, according to a new study.

"This study is important, as delirium is often overlooked and minimized in the hospital setting, especially in persons with dementia," study principal investigator Donna Fick, a professor of nursing at Penn State University, said in a university news release. "And it illustrates that delirium is deadly, costly and impacts patient functioning."

Delirium is a serious -- and usually sudden -- disturbance in a patient's thinking ability, involving confusion and disorientation. It often can be resolved if diagnosed and treated early.

Dementia, by contrast, is an irreversible, ongoing condition that affects both thinking and physical function, with symptoms such as memory loss, inability to solve simple problems, problems with language and thinking, and personality and behavior changes.

Fick and her colleagues looked at 139 hospitalized patients, aged 65 and older, with dementia and found that 32 percent of them developed delirium. The patients who developed delirium had a 25 percent increased risk of dying within 30 days.

In addition, patients with delirium stayed in the hospital about four days longer than those without delirium, had decreased levels of mental and physical abilities when they left the hospital and one month after discharge, and were more likely to have died a month after their hospital stay.

The study was published in the September issue of the Journal of Hospital Medicine.

Delirium can be caused by infections, dehydration and medication changes. Among the patients in this study, one-third were dehydrated when they arrived at the hospital.

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

More information

The U.S. National Library of Medicine has more about delirium.