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Investigators reported that people hospitalized for noncritical illness showed more cognitive decline in neuropsychological tests than people who were not hospitalized.
Older patients often emerge from the hospital with memory problems, attention and concentration difficulties, and other signs of cognitive decline — at least according to the patients themselves and their families. Now researchers analyzing data from thousands of patients 65 years of age and older have provided compelling evidence that hospitalization does in fact often result in their cognitive decline.
The research, conducted on people living in the Seattle area, builds on a small body of research that has found cognitive impairment in patients who survived hospitalization for critical illness.
Figure. THE NEW STUDY, conducted on people living in the Seattle area, builds on a body of research that has found cognitive impairment in patients who survived hospitalization for critical illness.
“We're talking about maybe 10 papers in the past 10 to 12 years that looked at about 500 patients,” said William J. Ehlenbach, MD, a fellow in pulmonary and critical care at the University of Washington in Seattle, the lead author of the Feb. 24 paper in the Journal of the American Medical Association (JAMA). These studies, however, examined patients only after they emerged from the hospital, which leaves open the possibility that their cognitive decline was underway before they were admitted, Dr. Ehlenbach said.
To verify that hospitalization for acute and critical illness triggers cognitive decline, Dr. Ehlenbach and colleagues examined data from the Adult Changes in Thought (ACT) study, an ongoing prospective longitudinal study of aging that includes members of the Group Health Cooperative 65 and older living in the Seattle area. All participants received the Cognitive Abilities Screening Instrument (CASI), a 100-point test which measures attention, concentration, orientation, short-term memory, long-term memory, language ability, visual construction, list-generating fluency, abstraction, and judgment. Dr. Ehlenbach's study included data on 2,929 individuals who had been evaluated at least twice, and were found to be free of dementia. He excluded participants who had been diagnosed with ischemic stroke, brain hemorrhage, head trauma, or other primary brain injury.
Of the remaining participants, 1,287 had one or more noncritical [non-intensive care] hospitalizations, and 41 had one or more critical hospitalizations. Those hospitalized for noncritical illness averaged one point lower on subsequent CASI scores than those not hospitalized. Those hospitalized for critical illness averaged 2.14 points lower on average. These declines mark a significant closing of the gap between 86, which suggests possible or probable dementia, and the group's baseline score of about 94, according to Dr. Ehlenbach. “Furthermore, demonstrating a small but significant difference in mean scores usually represents a much larger difference in a subset of exposed individuals,” he said.
In addition, they found a crude incidence of dementia of 14.6 cases per 1,000 person-years among those not hospitalized, 33.6 cases among those hospitalized for noncritical illness, and 31.1 cases among those hospitalized for critical illness.
The study, according to the authors, is the first to measure cognitive decline in older individuals before and after hospitalization, a comparison that suggests “an abrupt loss of cognitive function” rather than a mere acceleration of pre-existing cognitive impairment.
Dr. Ehlenbach suspects several factors may contribute to the cognitive decline, including delirium, glucose dysregulation, the administration of sedatives and analgesics, blood pressure dysregulation, and systemic inflammation caused by infection or general anesthesia. Underlying cerebrovascular disease or small vessel disease may also promote the decline, as well as preclinical neuropathological changes.
Although demonstrating a link between hospitalization and cognitive decline does not, in itself dictate changes in clinical care, Dr. Ehlenbach hopes the findings make clinicians more aware of the association.
Other researchers who have studied the relationship between acute illness and cognitive decline were excited that Dr. Ehlenbach had found a way to document mental status before and after hospitalization.
“I think it's a great paper,” said James C. Jackson, PsyD, assistant professor of medicine and psychiatry at Vanderbilt University, who has studied cognitive outcomes of ICU survivors for nearly a decade. “We have followed ICU survivors for up to a year, and we have identified rates of cognitive impairment of 30–60 percent, but we lacked hard data on how they functioned before, which has always been the Achilles heel of our research. This paper has data on the premorbid functioning of these patients, and I think the results are pretty compelling.”
These findings, according to Dr. Jackson, will require a different approach to older patients who complain about cognitive problems after hospitalization.
Figure. DR. WILLIAM J. EHLENBACH:“The science is fairly young, but those studies have pretty consistently shown that a substantial proportion of patients who were very sick and in the ICU have abnormal results on subsequent cognitive tests. Even a year or two down the line, the patients who were the sickest are still complaining about problems with concentration and mental processing speed.”
“Patients occasionally tell us, ‘I went to see my provider and told him I'm not as sharp cognitively as I was, and he told me don't worry about it, you're going to get better’,” Dr. Jackson said. “This offers some documentation that this is a real phenomenon and clinicians would be well served to attend to the complaints of their patients regarding cognitive issues.”
Now Dr. Jackson would like to see research that identifies the causes of cognitive decline in hospitalized patients. “This paper wasn't able to look in a granular way at the risk factors for this decline – for example, the association between delirium and the rate of cognitive decline, or the duration of mechanical ventilation, or the use of sedatives, and the rate of decline,” he said. “That's the Holy Grail in this — to figure out how we can intervene to reduce the risk of cognitive decline, and also how to rehabilitate the brains of these patients so they approach their baseline status to whatever extent is possible.”
He and colleagues have pilot tested a novel cognitive rehabilitation program in a small cohort of ICU patients. They anticipate publishing the results within the year.
Ramona O. Hopkins, PhD, who has done extensive research on cognitive impairment following acute respiratory distress syndrome and other critical illnesses, also praised Dr. Ehlenbach and colleagues for presenting solid data on the pre-morbid cognitive status of hospitalized patients. She noted that in her own research she has been able to link cognitive decline to serious illness, but has never been able to compare the results to pre-morbid status.
“If you've had a stroke or a brain injury you get referred for rehabilitation, but this group of patients does not, and that may be a profound oversight,” said Dr. Hopkins, professor of psychology and neuroscience and chair of the psychology department at Brigham Young University in Provo, UT, and a research consultant in the department of critical care medicine at Intermountain Medical Center in Salt Lake City.
“People have assumed that if you're sick and you get treated and go home you'll return to your previous level of functioning, but hospitalization actually can have a profound impact on brain function,” she said. “People may think this is just normal aging and decline, but it's not.”•
• Ehlenbach WJ, Hough CL, Crane PK, Haneuse SJ, Carson SS, Curtis JR, Larson EB. Association between acute care and critical illness hospitalization and cognitive function in older adults. 2010;303(8):763–70.