LONDON – Older adult patients who already had cognitive decline when they were admitted to a hospital often left with a significantly accelerated rate of decline, according to findings from a large longitudinal cohort study.

The study found up to a 62% acceleration of prehospital cognitive decline after any hospitalization. Urgent or emergency hospitalizations exacted the biggest toll on cognitive health, Bryan James, PhD, said at the Alzheimer’s Association International Conference.

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“There are some remaining questions, though, about what is driving this association,” said Dr. James of the Rush Alzheimer’s Disease Center, Chicago. “Is it the illness that brought the person into the hospital or procedures done there or something about the hospital environment that’s actually the cause of decline?”

Cognitive decline after hospitalization in older patients is a common occurrence but still poorly understood, he said. “Some data suggest this could actually be seen as a public health crisis since 40% of all hospitalized patients in the U.S. are older than 65, and the risk of past-hospitalization cognitive impairment rises with age.

“Given the risk to cognitive health, older patients, families, and physicians require information on when to admit to the hospital,” Dr. James said. “We wondered if those who decline rapidly after the hospital admission were already declining before. Our second question was whether elective hospital admissions are associated with the same negative cognitive outcomes as nonelective (emergent or urgent) admissions.”

To examine this, Dr. James and his colleagues used patient data from the Rush Memory and Aging Project, which provides each participant with an annual cognitive assessment consisting of 19 neuropsychological tests. They linked these data to each patient’s Medicare claims record, allowing them to assess cognitive function both before and after the index hospitalization.

The cohort comprised 930 patients who were followed for a mean of 5 years. Hospitalized patients were older (81 vs. 79 years). Most patients in both groups had at least one medical condition, such as hypertension, heart disease, diabetes, cancer, thyroid disease, head injury, or stroke. Cognition was already impaired in many of the hospitalized patients; 62% had mild cognitive impairment (MCI) and 35% had dementia. Among the nonhospitalized subjects, 49% had MCI and 24% had dementia.

Of the cohort, 66% experienced a hospitalization during follow-up. Most hospitalizations (57%) were either for urgent or emergency problems. The rest were elective admissions. The main outcome was change in global cognition – an averaged z-score of all 19 tests of working memory, episodic memory, semantic memory, visuospatial processing, and perceptual speed.

Elective admissions were mostly planned surgeries (94%), and unplanned surgeries occurred in 64% of the nonelective admissions. Most of the elective admissions (81%) involved anesthesia, compared with 32% of the nonelective admissions. About 40% of each group required a stay in the intensive care unit. Around 11% in each group had a critical illness – a stroke, hemorrhage, or brain trauma in about 6% of each group.

A multivariate analysis looked at the change in cognition during two time points: 2 years before the index hospitalization and up to 8 years after it. As could be expected of aged subjects in a memory study cohort, most patients experienced a decline in cognition over the study period. However, nonhospitalized patients continued on a smooth linear slope of decline. Hospitalized patients experienced a significant 62% increased rate of decline, even after controlling for age, education, comorbidities, depression, Activities of Daily Living disability, and physical activity.

Visuospatial processing was the only domain not significantly affected by a hospital admission. All of the memory domains, as well as perceptual speed, declined significantly faster after hospitalization than before.

The second analysis examined which type of admission was most dangerous for cognitive health. This controlled for even more potential confounding factors, including length of stay, surgery and anesthesia, Charlson comorbidity index, critical illness, brain injury, and number of hospitalizations during the follow-up period.

Urgent and emergency admissions drove virtually all of the increase in decline, Dr. James said, with a 60% increase in the rate of decline, compared with the prehospitalization rate. Patients who had elective admissions showed no variance from their baseline rate of decline, and, in fact, followed the same slope as nonhospitalized patients. Again, change was seen in the global score and in all the memory domains and perceptual speed. Only visuospatial processing was unaffected.

“It’s unclear why the urgent and emergent admissions drove this finding, even after we controlled for illness and injury severity and other factors,” Dr. James said. “Obviously, we need more research in this area.”

He had no financial disclosures.

msullivan@frontlinemedcom.com

On Twitter @alz_gal

Hospitalizations may speed up cognitive decline in older adults