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Neurology Today:
doi: 10.1097/01.NT.0000413861.80740.bf
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Hospitalization Associated with Cognitive Decline in Elderly Adults, Study Finds

Rukovets, Olga

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For older adults, going to the hospital may be bad for your health, according to an observational study published March 21 online before the print issue of Neurology. The population-based study from the Rush University Medical Center found that older adults who are hospitalized experience accelerated cognitive decline compared with those adults who are not — irrespective of the severity of their illness or the length of their hospital stay.

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Lead author, Robert S. Wilson, PhD, the senior neuropsychologist of the Rush Alzheimer's Disease Center, and colleagues used data from the Chicago Health and Aging Project, a longitudinal study of aging and dementia based in three neighborhoods in Chicago. “Our question was whether after hospitalization your path of cognitive change shifted at all. And the answer that we received was rather surprising — we found that there was, on average, approximately a 2.5-fold increase in the rate of cognitive decline in people following their initial hospitalization during our study period,” he told Neurology Today.

Barry W. Rovner, MD, professor in the departments of psychiatry and neurology at Jefferson Hospital for Neuroscience in Philadelphia, who was not involved in this research, said it was a great study. “The findings are congruent with recent research and what clinicians have observed. It shows that there are aspects to hospitalization that contribute to cognitive decline, even if it saves your life,” he said.

DR. ROBERT S. WILSON...
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STUDY PROTOCOLS

Investigators pulled data from a geographically-defined region on the south side of Chicago, Dr. Wilson said. “In the early 1990s we did a complete census of this area and identified everyone over the age of 65.” Interviews with this population of older adults have since continued at three-year intervals, and include tests for cognitive function, among other things, using three separate assessments: the mini-mental state examination (MMSE), the episodic memory score, and the executive function score.

This study looked at people who had been involved for at least six years, using Medicare records to track hospitalization — they did not have access to reason(s) for hospitalization. 1,870 individuals were included, and their cognitive assessments were completed 3 to 5 times at each interval. Of the study population, 1,335 persons (71.4%) were hospitalized at least once during the 9.3 year period.

The authors found that the rate of cognitive decline after hospitalization was not related to the level of cognitive function at study enrollment (r= 0.01, p=0.88) but was moderately correlated with rate of cognitive decline before hospitalization — the time from study enrollment to first hospitalization — (r=0.55, p=0.021). They tested the association of more severe illness, longer hospital stay, and older age, and found that none of them accounted for the rate of decline after hospitalization. Dr. Wilson told Neurology Today that they identified many aspects of personality and lifestyle that seem to be related to cognitive decline in old age, and tried “as best as we could to control for those factors, so that any effect here with hospitalization seems different from those effects.”

Those who were sicker and had longer hospital stays experienced more rapid decline following hospitalization, they wrote, which suggested that severity of the illness requiring hospitalization may have contributed to accelerated cognitive decline. The association was relatively weak, however, implying that other factors were also involved. Older age and more rapid prehospital rate of cognitive decline were also related to post-hospital decline, the authors found, and those people who were showing evidence of cognitive decline before the hospital seemed particularly vulnerable to the effect of hospitalization in our study, Dr. Wilson said. “One thought that we had was that hospitalization is a very stressful experience, and it may in some sense unmask pre-existing cognitive symptoms.”

Cognitive dysfunction is a complication of critical illness and surgical procedures, and delirium, which has been linked with cognitive impairment, affects between 25 and 60 percent of those undergoing surgery, Dr. Wilson and colleagues wrote. In this study, “only 3% of hospitalizations involved a critical illness, but 15%-20% of older general medical inpatients are estimated to meet delirium criteria and it is likely that many more exhibit subsyndromal signs of delirium,” which suggests that acute brain dysfunction during hospitalization also contributed to the post-hospital decline.

One of the take-home messages here, Dr. Wilson said, is that we need to be very aware of the cognitive status of older people — both those who are already in the hospital and those who we are considering hospitalizing.

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EXPERTS COMMENT

Constantine Lyketsos, MD, MHS, the director of the Memory and Alzheimer's Treatment Center at Johns Hopkins, and the Althouse Professor in Alzheimer's Disease Research, said this was a methodologically sound study with a good sample size and good follow-up, as well as conclusions that “resonate with what we know from other studies.” He cited an article in the Jan. 12 edition of the Journal of the American Medical Association (JAMA), which showed that incident dementia was significantly associated with increased risk of hospitalization for medical illnesses usually managed in ambulatory care settings.

Delirium is likely a key factor in the post-hospitalization decline, Dr. Rovner said. Given the limited information that Medicare records provide, the study could not control for delirium and the factors that increase its risk. It would be important to know why people were hospitalized — dehydration, infection, too many medications. For example, he added, benzodiazepines are commonly used in hospitals as sleep medicines and they may precipitate delirium, he told Neurology Today.

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We can't be sure of the nature of the association from this study, Dr. Lyketsos said: “It could simply be that being in the hospital leads to detecting symptoms that were already happening. So the role of the hospital in that regard is good. The other possibility — and they are not mutually exclusive — is the stress of the hospitalization or the stress leading to the hospitalization brings dementia on by acting on a vulnerable brain. The way that physicians can be more vigilant would be to make a large effort to pick up dementia early on — even in its mildest form — so that hospitalizations can be prevented, which was the point from the JAMA article, and hospitalization can also be managed in older persons so as not to have big effects on cognition,” he said.

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HOW TO ADDRESS COGNITIVE DECLINES IN IN-PATIENTS

What can physicians do to address the issue of cognitive declines in patients who are hospitalized? Ultimately, said Robert S. Wilson, PhD, the senior neuropsychologist of the Rush Alzheimer's Disease Center, we need to try to understand why older people seem to be coming out of the hospital with poorer cognitive function than when they went in — if it's not explained by the conditions that brought them there in the first place.

Constantine Lyketsos, MD, MHS, the director of the Memory and Alzheimer's Treatment Center at Johns Hopkins, and the Althouse Professor in Alzheimer's Disease Research, said several unanswered questions remain: “Is it because of the hospital itself — so could we improve, for example, how elderly patients sleep in the hospital? Could we reduce the amount of medications that they get? Both lack of sleep and medications could provoke the onset of cognitive symptoms. What is it that we could understand about the causal links here which have not been established? That will then guide us to see if there's something we actually can do.”

If doctors were more sensitive to monitoring older persons for preventable or treatable conditions that stem from like poor medication management, signs of congestive heart failure, poor management of diabetes and urinary tract infections, then hospitalization could be prevented, said Barry W. Rovner, MD, professor in the departments of psychiatry and neurology at Jefferson Hospital for Neuroscience in Philadelphia. If patients are in fact hospitalized, doctors and neurologists must do everything in their power to prevent or reduce the severity of delirium.

—Olga Rukovets

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REFERENCES:

• Wilson RS, Hebert LE, Evans DA, et al. Cognitive Decline after Hospitalization in a Community of Older Persons. Neurology 2012; E-pub 2012 Mar. 21.

• Phelan EA, Borson S, Larson EB, et al. Association of incident dementia with hospitalizations. JAMA 2012;307(2):165–172.

©2012 American Academy of Neurology

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