Progressive cognitive impairment is Alzheimer's disease is characterized by

Memory impairment is typically an early and prominent feature in dementia, especially in dementias involving the coex, such as dementia of the Alzheimer's type. Early in the course of dementia, memory impairment is mild and usually most marked for recent events. As the course of dementia progresses, memory impairment becomes severe, and only the earliest learned information (e.g., a person's place of bih) is retained. Reference: Kaplan & Sadock's Synopsis of Psychiatry: Behavioral Sciences/Clinical Psychiatry, 11th Edition, page 712.