May 6 (HealthDay News) -- The delirium sometimes experienced by people with Alzheimer's who are hospitalized might accelerate their cognitive decline, a new study shows.
Researchers found that people with Alzheimer's who had an episode of delirium while in the hospital had a rate of cognitive decline that was three times faster than that of those who didn't experience delirium.
"From a clinical standpoint, this study suggests that over 12 months, patients with AD [Alzheimer's disease] who become delirious experience the equivalent of an 18-month decline compared to those who do not experience delirium," the study's authors wrote.
What might an 18-month decline in cognitive ability signify for the average person with Alzheimer's? That can vary depending upon the individual, according to Dr. Tamara D. Fong, an instructor of neurology at Harvard Medical School and the study's lead author.
For example, someone who is mildly forgetful about the details of a conversation might not, 18 months later, be able to drive, balance a check book or recognize relatives not frequently seen, Fong said.
But there was good news in the findings as well.
"Delirium is preventable, so we can actually design an intervention for a disease for which we have no cure at the present time," she said. Prevention strategies would probably involve multiple components, Fong said, including such things as making sure people with Alzheimer's who are hospitalized have their glasses and hearing aides on so that they remain as oriented as possible and keeping them out of the hospital by foregoing elective surgeries.
Further training about delirium for hospital staff also might help. "Delirium is sometimes hard to diagnose and probably is under-recognized, even in a hospital setting," she said.
The study, published in the May 5 issue of Neurology, compared the speed of cognitive decline among 408 people with Alzheimer's, 72 of whom developed delirium during the course of their illness.
Delirium is a state of extreme confusion that occurs suddenly and can be short-lived or more long-term. "It usually develops in the context of infections, hospital surgeries and medication changes," Fong said.
This could put the value of elective surgery for people with Alzheimer's into question, she said, adding that further research might be needed to evaluate the risk/benefit ratio. Also, Fong said, because surgery and anesthesia remain big risk factors for delirium, it might be better to rely on an epidural rather than general anesthesia for people with Alzheimer's who have hip replacement surgery.
Dr. Gary Kennedy, director of geriatric psychiatry at Montefiore Medical Center in New York City, speculated that better control over anesthesia might boost the safety of elective surgeries for people with Alzheimer's. "This implies that if you're especially vigilant about preventing delirium, maybe those elective hospitalizations are a bit safer after all," he said.
Some sleep medications, antihistamines and antibiotics as well as anesthetics also have been associated with higher risk for delirium, Fong added.
Kennedy is hopeful that future research will look at the difference between people with Alzheimer's who are hospitalized for elective procedures, such as hip or knee replacement, and those who are hospitalized via the emergency room because of an illness. That distinction might help clarify what impact illness has on the development of delirium, he explained.
SOURCES: Tamara D. Fong, M.D., Ph.D., instructor, neurology, Harvard Medical School, and clinical neurologist, Beth Israel Deaconess Medical Center, Boston; Gary J. Kennedy, M.D., director, geriatric psychiatry, Montefiore Medical Center, New York City; May 5, 2009, Neurology