Dementia develops over time, with a slow progression of cognitive decline. Delirium occurs abruptly, and symptoms can fluctuate during the day. The hallmark separating delirium from underlying dementia is inattention. The individual simply cannot focus on one idea or task.
Delirium often is unrecognized by healthcare professionals because changes in behavior in persons with dementia (such as agitation or sun downing) may be attributed to the dementia disease process, versus an acute problem.
Delirium may be the first and perhaps only clue of medical illness or adverse medication reaction in an individual with Alzheimer’s.
Often, persons with dementia develop delirium while hospitalized. One study found that one-quarter of Alzheimer’s patients developed delirium during a hospital admission.