Inflammation appears to play a prominent role in the onset of delirium in older patients, according to a new study at Beth Israel Deaconess Medical Center (BIDMC). The findings may help clinicians identify patients at greatest risk of developing delirium and aid in the treatment of the condition, which occurs in up to 64 percent of hospitalized seniors.
Anything that causes tissue injury, including infection or illness as well as surgery, can activate various immune cells and cause inflammation.
“Delirium may be an inflammatory response gone awry,” said co-senior author Edward Marcantonio, M.D., Professor of Medicine at Harvard Medical School (HMS).
“Delirium is the most common complication among hospitalized elders. Once widely assumed to be a short-term, transient condition, there is now evidence that delirium and its effects can last long after patients have left the hospital,” he says.
In fact, older patients who develop delirium have a two to three times greater risk of developing dementia.
The researchers found that older patients with delirium had significantly higher levels of the inflammatory marker interleukin-6 (IL-6) two days after surgery. They also found elevated levels of interleukin 2 (IL-2).
“With strong evidence for the involvement of IL-6 and evidence for the involvement of IL-2 in patients with delirium, it appears that inflammation is indeed a basic mechanism underlying this condition,” said Marcantonio, also the Director of the Aging Research Program in the Division of General Medicine and Primary Care at BIDMC.
For the study, BIDMC researchers and co-lead authors Sarinnapha M. Vasunilashorn, Ph.D., and Long Ngo, Ph.D., examined data from a patient cohort called SAGES (Successful Aging after Elective Surgery Study). Sponsored by the National Institute on Aging, the researchers have been following 566 noncardiac surgical patients over the age of 70 for the past five years with the goal of finding new approaches to prevent delirium and its long-term consequences in older adults.
“In examining SAGES patients who had undergone major elective surgery, we compared patients who developed delirium with those who did not,” explained Vasunilashorn, a postdoctoral fellow in the Division of General Medicine and Primary Care at BIDMC and HMS.
Surgery types included orthopedic, vascular, and gastrointestinal procedures.
“The results showed that levels of IL-6 were significantly elevated in the delirium patients two days after surgery,” said Vasunilashorn. “The magnitude of difference in levels of IL-6 between delirious and non-delirious patients was about 10 times the upper limit for normal levels in older adults.”
Delirious patients also had higher levels of IL-2 compared to non-delirious patients. The role of IL-2 in delirium is a new finding, said Vasunilashorn, and it is particularly interesting since it has been linked to blood-brain barrier dysfunction in animal studies.
The study findings may lead to new preventative measures and treatments for delirium.
“We want our patients to get better, not worse, after a hospitalization. Understanding the role that inflammation plays in the onset of delirium can help us identify patients who may be at highest risk of developing this condition, and take steps to reduce their risk,” said Marcantonio.
The study is published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences.