A 68 year old man is admitted to the hospital for delirium associated with a urinary tract infection. Upon adequate treatment of the infection, the patient's mental status improved significantly, though he is noted to remain paly disoriented. He also has an impairment in sho-term memory, difficulties in naming simple objects, and impaired concentration. His family members confirm an 8-month history of gradual progressive decline in cognitive abilities, which they attribute to old-age. However, the man is no longer able to manage his finances and has gotten lost while driving to the grocery store on two occasions. Prior to discharge from the hospital, the nursing staff repos that the patient continues to have urinary incontinence, though his infection has resolved. He is also noted to have a very unsteady gait, requiring assistance when walking. No other obvious signs or symptoms are present. Which disorder most likely accounts for this patient's dementia?