Figure 3. Over the clinical course of AD, patients will demonstrate progressive declines in functional ability that correlate with MMSE scores. In the preclinical phase, also called MCI, patients with MMSE score greater than 23 will demonstrate minimal impairment—generally, mild memory loss—while functioning normally and independently. The typical length of the MCI phase remains undetermined. Onset of mild AD is indicated by MMSE score of 20-23; these patients exhibit gradual alterations in cognition, function, behavior, and mood. Forgetfulness and repetitive questions are hallmarks; daily function begins to become impaired. In moderate AD (MMSE score of 10-19), cognitive impairments progressively deteriorate and now include short-term memory loss (eg, difficulty in recalling recent conversations, forgetting to keep appointments, inability to remember recent events). Patients begin to have trouble with verbal fluency; specifically, increasing difficulty in remembering the correct word. Severe stage is reached when MMSE scores decline to less than 10. At this point, patients exhibit behavioral changes that include agitation, delusion, aggression, wandering, and hallucination. Sleep patterns are altered, and the patient eventually becomes completely dependent on others for dressing, feeding, and bathing. The clinical progression from onset of mild AD to onset of severe AD, although variable, is about 10 years.