Traditional diagnostic criteria for Alzheimer disease include all of the following: Dementia established clinically and documented by a formal mental status examination Deficits in ≥ 2 areas of cognition Gradual onset (ie, over months to years, rather than days or weeks) and progressive worsening of memory and other cognitive functions No disturbance of consciousness Onset after age 40, most often after age 65 No systemic or brain disorders (eg, tumor, stroke) that could account for the progressive deficits in memory and cognition However, deviations from these criteria do not exclude a diagnosis of Alzheimer disease, particularly because patients may have mixed dementia.