An 80-year-old male with a history of Alzheimer's dementia is admitted to the hospital for pneumonia. On hospital day 2, his family reports he is increasingly confused, disoriented to place and time, and has episodes of agitation throughout the day, particularly at night. This change occurred suddenly overnight. His vital signs are stable. Which of the following is the most distinguishing feature differentiating his current condition from his baseline dementia?
✓ Correct Answer: Option B
The acute onset and fluctuating course (worse at night, periods of agitation) are classic features of delirium, distinguishing it from the chronic, progressive, and generally stable (though worsening over time) course of dementia. Memory impairment, executive dysfunction, and impaired ADLs can be present in both.