Approximately one in eight Alzheimer’s disease patients who develop delirium while hospitalized will suffer at least one adverse outcome, based on data from 771 adults. The findings were published in Annals of Internal Medicine on June 18.

Previous studies have shown that delirium can increase the rate of cognitive decline in AD patients, but the impact of hospitalization and delirium has not been well studied, said Dr. Tamara G. Fong of the Aging Brain Center, Boston, and her colleagues. Adults with Alzheimer’s disease (AD) are three times more likely to be hospitalized than are those without AD, the researchers noted.

To assess the adverse outcomes of death, institutionalization, and cognitive decline associated with hospitalization and delirium, Dr. Fong and her colleagues followed 771 community-dwelling adults aged 65 years and older with a clinical diagnosis of AD. The mean follow-up was 2 years, and outcomes were assessed at 1 year after an initial hospitalization. A total of 367 individuals (48%) were hospitalized, and 194 of these patients (25%) developed delirium while hospitalized (Ann. Intern. Med. 2012;156:848-56).

At least one adverse outcome occurred in 32% of nonhospitalized patients, 55% of hospitalized patients without delirium, and 79% of hospitalized patients with delirium.

In the hospitalized patients, 6% of deaths, 15% of institutionalizations, and 21% of cases of cognitive decline were associated with delirium, the researchers said.

Death occurred in 15% of hospitalized patients with delirium, compared with 9% of hospitalized patients without delirium and 2% of nonhospitalized patients.

The hospitalized patients with delirium had an increased risk for death, institutionalization, and cognitive decline, compared with the other groups, with adjusted risk ratios of 5.4, 9.3, and 1.6, respectively. Hospitalized patients with no delirium had a slightly smaller increase in the risk of death (adjusted risk ratio 4.7) and institutionalization (adjusted risk ratio 6.9).

The mean age of the patients was 77 years, 57% were women, and 95% were white.

The results were limited by several factors, including the observational nature of the study and the incomplete data on the cognitive outcome and functional status of some patients, the researchers wrote. But the findings show “the important and incremental associations of hospitalization and delirium with 1-year outcomes,” they said.

Additional research is needed to determine whether preventing hospitalization and delirium in AD patients can reduce their risk for death, institutionalization, and cognitive decline, they noted.

Dr. Fong had no financial conflicts to disclose. The study was funded by the National Institute on Aging and the Massachusetts Alzheimer’s Disease Research Center.