Different meanings of a three-point decline in MMSE score in Alzheimer's disease and depressive disorder.

Our results indicate that memory performance is the most important measure of disease severity and the main contributor to the decline in MMSE score at onset of clinical manifestation of Alzheimer's disease. In general, this suggests that memory should be the primary measure used in routine clinical care and the primary endpoint in clinical trials involving patients with Alzheimer's disease at onset of clinical manifestation. Changes in other measures of cognition should prompt consideration of possible comorbidities as a cause, rather than the impact of Alzheimer's disease itself.