August 21, 2012 — Harmful effects of hospital-acquired delirium on cognitive function linger for years in patients with Alzheimer's disease (AD), a new study shows.
Investigators found that delirium in patients with AD was independently associated with cognitive deterioration up to 5 years after hospitalization at a rate roughly 2-fold greater than that seen in patients with AD who did not develop delirium while hospitalized.
"Delirium is commonly thought of as a transient condition that is reversible in patients with AD," first author Alden Gross, PhD, MHS, of the Aging Brain Center, Institute for Aging Research, Hebrew SeniorLife in Boston, Massachusetts, told Medscape Medical News.
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Dr. Alden Gross |
"The results of our study suggest that, in fact, delirium is associated with an accelerated pace of cognitive deterioration over a much longer period, for up to 5 years following hospitalization. Ours is the first study we are aware of to show this using such a long follow-up period," Dr. Gross noted.
The study was published online August 20 in Archives of Internal Medicine.
More Rapid Decline
Using the Massachusetts AD Research Center (MADRC) patient registry, Dr. Gross and colleagues evaluated the rate of cognitive deterioration for up to 5 years before and 5 years after a hospital stay in 263 adults with preexisting AD. Cognitive function was measured using the information-memory-concentration (IMC) section of the Blessed Dementia Rating Scale.
A total of 148 participants developed delirium while hospitalized (56.3%; 95% confidence interval [CI], 50.2% - 62.3%). The researchers say that the rate of cognitive deterioration before hospitalization did not differ significantly between patients who developed delirium and those who did not (P = .24).
After adjustments were made for dementia severity, comorbidity, and demographic factors, patients who developed delirium showed greater cognitive decline during the year after hospitalization (3.1 IMC points/year; 95% CI, 2.1 - 4.1) relative to patients who did not develop delirium (1.4 IMC points/year; 95% CI, 0.2 - 2.6).
"The ratio of these changes suggests that cognitive deterioration following delirium proceeds at twice the rate in the year after hospitalization compared with patients who did not develop delirium," Dr. Gross and colleagues report.
In addition, investigators found that patients who developed delirium in the hospital maintained a more rapid rate of cognitive deterioration throughout a 5-year period after their hospital stay. "Sensitivity analyses that excluded rehospitalized patients and included matching on baseline cognitive function and baseline rate of cognitive deterioration produced essentially identical results," the authors note.
Medical Emergency
"If delirium worsens the long-term course of cognitive function among persons with AD, as our study suggests, it should be handled as a genuine medical emergency, meriting changes to incorporate routine delirium prevention in the standard practice for dementia patients to ensure timely intervention to prevent long-term cognitive deterioration," said Dr. Gross.
He said the fact that delirium developed in 56% of patients in the study underscores its importance, "but delirium is recognized by physicians and nurses in fewer than 30% of hospital patients, so ongoing clinician education is needed."
Dr. Gross said the widespread availability of brief cognitive screening tests can help to improve delirium screening at the bedside. "For high-risk patients, application of tested protocols, such as reorientation, therapeutic activities, mobility, hydration, and other elements from the Hospital Elder Life Program (HELP) may help to prevent delirium."
Commenting on the findings for Medscape Medical News, Eduard E. Vasilevskis, MD, coauthor of a linked commentary, said the study serves as "an alarm to the long-term dangers of acute illness and more specifically delirium on the development and/or progression of long-term cognitive impairment."
"We can no longer be blind to the presence of delirium and must implement validated measures that are reliably measured at the bedside," Dr. Vasilevskis and coauthor E. Wesley Ely, MD, MPH, from Vanderbilt University and the Geriatric Research, Education, and Clinical Center in Nashville, Tennessee, write.
Dr. Vasilevskis agreed that routine screening for delirium is an "important first step for identifying patients at risk and understanding the magnitude of the problem. This should be accompanied by implementation of nonpharmacologic protocols that have been shown to prevent delirium, such as early mobility programs, but are still underutilized," he said.
Multiple Populations Affected
The independent effects of delirium on long-term cognitive impairment have now been seen in multiple populations, including surgical and intensive care patients.
For example, as reported by Medscape Medical News, a study published in the Journal of the American Medical Association in 2010 showed that older adults hospitalized with acute or critical illness were at increased risk for cognitive decline. In addition, individuals hospitalized with a noncritical illness were more likely to develop incident dementia.
More recently, a study published in Neurology in March of this year and reported by Medscape Medical News showed that older adults have a 2.4-fold increase in the rate of cognitive decline after hospitalization — an increased risk that persisted after illness severity and length of stay were accounted for.
Just this past June, as reported by Medscape Medical News, Dr. Gross and colleagues presented in Annals of Internal Medicine evidence indicating that patients with AD who require a hospital stay are at increased risk for further cognitive decline, institutionalization, and death in the year following the hospital stay, with risks greatest in those who developed delirium.
"We should not wait for delirium to happen but must work to implement proven interventions that prevent delirium," Dr. Vasilevskis and Dr. Ely write in their commentary.
"[We] must continue to find ways to treat delirium that include focus on comorbid disease management, removal of offending medications, and environmental modifications. We must also develop ways to rehabilitate the brain following acute illnesses so as to mitigate the long-term cognitive decline associated with delirium."
This study was supported by the National Institute on Aging. The authors have disclosed no relevant financial relationships. Dr. Vasilevskis has disclosed no relevant financial relationships. Dr. Ely has disclosed that he received grant support and honoraria from Eli Lilly, Hospira, and Pfizer.
Arch Intern Med. Published online August 20, 2012.