Hospitalization linked to cognitive decline

Older adults with critical illness suffer impairment

Older patients hospitalized for acute care or a critical illness are more likely to experience cognitive decline compared to older adults who are not hospitalized, according to a study in the Feb. 24, 2010, issue of the Journal of the American Medical Association.1

Although previous studies suggested that survivors of critical illness suffer long-term cognitive impairment, no study had previously measured cognitive function before a critical illness.

Researchers analyzed data from a study that was conducting cognitive testing on older adults, and examined administrative data from hospitalizations to determine whether hospitalizations for acute illness or critical illness were associated with cognitive decline and dementia. The study included data from 1994 through 2007 on 2,929 individuals 65 years old and older without dementia at the beginning of the study.

During an average follow-up of 6.1 years, 1,601 participants had no hospitalizations while enrolled in the study; 1,287 study participants were hospitalized for non-critical illness; and 41 participants were hospitalized for a critical illness.

There were 146 cases of dementia among those never hospitalized during the study. Among those experiencing one or more non-critical illness hospitalizations but no critical illness hospitalizations during study participation, there were 228 cases of dementia. There were five cases of dementia among those experiencing one or more critical illness hospitalizations during the study.

The researchers found that patients who had a hospitalization for an acute care or critical illness had lower CASI scores at follow-up compared to those who were not hospitalized. Also, after adjusting for various factors, patients hospitalized for a non-critical illness had a 40% higher risk of dementia.

The researchers add that the mechanisms through which critical illness may contribute to neurocognitive impairment are multiple, with evidence suggesting that hypoxemia (decreased partial pressure of oxygen in blood), delirium, hypotension, glucose dysregulation, systemic inflammation, and sedative and analgesic medications all may potentially play a role.

The authors conclude, "Among a cohort of older adults without dementia at baseline, those who experienced acute care hospitalization and critical illness hospitalization had a greater likelihood of cognitive decline compared with those who had no hospitalization."

Reference

1. Ehlenbach WJ, Hough CL, Crane PK, et al. "Association between acute care and critical illness hospitalization and cognitive function in older adults" JAMA 2010;303[8]:763-770.