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Delirium and Alzheimer Disease: A Dangerous Duo

Cognitive decline accelerates in patients with AD who experience delirium.

A long-standing clinical pearl is that brain injury increases an individual’s vulnerability to the cognitive effects of certain medications and diseases (e.g., infection) and that when the offending agent is removed or the disease has been treated, the individual recovers. To learn whether this is true for delirium in patients with Alzheimer disease, researchers conducted a large prospective study of consecutive patients from a memory-disorders unit in a large academic hospital. The patients were diagnosed with probable or possible AD and were reassessed approximately every 6 months. Of 990 eligible patients, 72 had experienced episodes of delirium, diagnosed through in-hospital chart reviews, at time points allowing for determination of the postdelirium trajectory of cognitive decline; 336 patients without delirium episodes formed the comparison group.

Those with delirium were older (77 vs. 73), more likely to be male (54% vs. 41%), and more likely to have a family history of dementia (11% vs. 4%). Delirium patients also had less education (13 vs. 14 years), more comorbid illnesses (1.7 vs. 1.3), and a shorter duration of symptoms before AD diagnosis (2.6 vs. 3.2 years). The postdelirium group was less cognitively impaired than the nondelirium group. Subsequent analyses controlled for these group differences.

In the postdelirium group, the rate of cognitive decline (measured by a test of information, memory, and concentration) accelerated significantly within 6 months. This rate was approximately three times faster than in the nondelirium group.

Comment: The authors state that patients with delirium experienced the equivalent of an 18-month decline in 12 months — a difference greater than the therapeutic effect reported for acetylcholinesterase inhibitors. Having other risk factors (e.g., older age, more medical comorbidity) increases the vulnerability. Few strategies to prevent delirium have been studied in these at-risk patients. Still, prevention and early identification might have long-lasting consequences for their quality of life.

— Jonathan Silver, MD

Published in Journal Watch Psychiatry May 4, 2009

Citation(s):

Fong TG et al. Delirium accelerates cognitive decline in Alzheimer disease. Neurology 2009 May 5; 72:1570.

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• Report of the Obvious
  Tina A Dobsevage, 5 May 2009 11:58 AM EST
  Presumably people with Alzheimer's have a progressive degenerative neurological disease which never improves significantly even with Aricept, etc. Delirium is... [more]
• Reply to Dr. Dobsevage
  Lisa A Leinau, Cheshire Medical Center/Dartmouth-Hitchcock Keene, 2 Jun 2009 9:17 PM EST
  While pre-existing cognitive impairment is a risk factor for delirium, people without cognitive impairment also become delirious in the context... [more]