Final answer:
The rapid onset and fluctuating course of symptoms are key characteristics distinguishing delirium from dementia, such as Alzheimer's disease, which has a gradual, progressive cognitive decline.
Step-by-step explanation:
When trying to distinguish between delirium and dementia, the most helpful characteristic is the onset of symptoms. Delirium typically presents with a rapid onset of symptoms and a fluctuating course, while dementia often develops slowly and progressively over time.
Symptoms of Alzheimer's disease, a common form of dementia, include disruptive memory loss, confusion about time or place, difficulty planning or executing tasks, poor judgment, and personality changes. In contrast, delirium may be characterized by significant fluctuations in attention and cognitive function, often developing over a short time and tending to fluctuate throughout the day.
The rapid onset and fluctuating course of symptoms are more characteristic of delirium, while the gradual, progressive decline is indicative of dementia.