A 72-year-old woman with Alzheimer's dementia is admitted to the hospital for pneumonia. Over the past 24 hours, she has become increasingly agitated, disoriented to time and place, and her family reports her confusion worsens in the evening and improves in the morning. Her vital signs show fever (38.5°C) and tachycardia. Which of the following is NOT consistent with superimposed delirium in this patient?