Published on: August 21, 2012
by Nancy Walsh for MedPage Today:
Patients with Alzheimer’s disease who develop delirium while hospitalized — a common and preventable occurrence — saw worsening of their dementia, researchers found.
Patients who experienced an episode of hospital-associated delirium had a 2.2-fold increase in the rate of cognitive decline during the subsequent year, and a 1.7-fold annual increase during 5 years after the episode, according to Alden L. Gross, PhD, of Hebrew SeniorLife in Boston, and colleagues.
The deterioration was significantly greater in the delirium group at a difference of 1.7 information-memory-concentration (IMC) points per year (95% CI 0.3 to 3.1), and remained that way through the end of the study period (P=0.003), the researchers reported online in Archives of Internal Medicine.
“Our results challenge the notion that delirium is transient and reversible in [Alzheimer’s disease],” they observed. Delirium has been estimated to occur in 20% of older hospitalized patients and at three times that rate among those with Alzheimer’s disease.
That delirium has adverse cognitive consequences for patients without dementia has previously been demonstrated, but only short-term effects have been assessed in patients with Alzheimer’s disease.
To examine the longer-term effects, Gross and colleagues analyzed data from a longitudinal Alzheimer’s disease registry, identifying 148 patients who had an episode of delirium in the hospital and 115 who were hospitalized but remained delirium-free.
A majority of the patients were women with a mean age of 78.3 years. Patients in the registry were seen every 6 months, with an average of two clinic visits before hospitalization and three subsequently, with a duration of up to 5 years.
The incidence of delirium overall was 56.3% (95% CI 50.2 to 62.3). A total of 45.2% of the patients died, and 23.6% were lost to follow-up. Compared with patients in the no delirium group, those in the delirium group were more likely to be male with fewer years of education, as well as married and with a history of smoking. They also demonstrated greater cognitive impairment at the baseline visit.
Baseline scores on the IMC component of a dementia rating scale, after adjustment for confounders such as severity and duration of dementia, education, and comorbidities, did not differ significantly between the dementia and no-dementia groups.
During the year after the hospitalization, patients with dementia had a 3.1-point (95% CI 2.1 to 4.1) decline on the rating scale, compared with a 1.4-point (95% CI 0.2 to 2.6) decline among patients without dementia.
Through long-term follow-up of up to 5 years, the declines in the two groups were 3.1 points (95% CI 2.5 to 3.7) and 1.9 points (95% CI 1.4 to 2.4), respectively.
“This finding suggests that delirium may fundamentally alter the cognitive trajectory in a sustained fashion,” the researchers stated.
They pointed out certain limitations of the analysis, such as the semi-annual assessments, which might not have reflected the full extent of the impact of delirium, and reliance on medical record review for diagnosis of delirium.
In addition, delirium was probably underestimated, because of a common belief that hospital-associated delirium is unavoidable and inconsequential.
“If delirium worsens the long-term course of cognitive function among persons with [Alzheimer’s disease], it should be handled as a genuine medical emergency, meriting changes to incorporate routine delirium prevention in the standard practice for patients with dementia,” Gross and colleagues stated.
Preventive strategies included activities with therapeutic potential and attention to critical concerns such as hydration and mobility, they noted.
In an invited commentary, Eduard Vasilevskis, MD, and E. Wesley Ely, MD, of Vanderbilt University in Nashville, agreed with the importance of preventive measures.
“We can no longer be blind to the presence of delirium and must implement validated measures that are reliably measured at the bedside,” they wrote.
While clinicians have long thought that patients who develop acute delirium while hospitalized have sustained changes in cognitive function, the findings of Gross and colleagues confirm this.
“This study stands as a stark warning of the potential long-term dangers of hospitalization and delirium,” Vasilevskis and Ely cautioned.
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