At baseline and annually thereafter, subjects in each study underwent a uniform structured clinical evaluation that included a medical history, complete neurological examination, and cognitive performance testing. Based on these data and in-person evaluation of the subjects, an experienced clinician diagnosed dementia and AD using the criteria of the joint working group of the National Institute of Neurologic and Communicative Disorders and Stroke and the Alzheimer Disease and Related Disorders Association.12 The criteria require a history of cognitive decline and impairment in at least 2 cognitive domains, one of which must be memory for a diagnosis of AD. As previously described,13 impairment in 5 cognitive functions (orientation, attention, memory, language, and visuospatial ability) was determined in a 2-step process. First, an algorithm rated impairment in each area of function based on educationally adjusted cutoff scores on 11 individual tests.14 Second, based on all test data and information on education, sensorimotor problems, and effort, a neuropsychologist agreed or disagreed with each rating and supplied a new rating in the event of disagreement. Persons who had cognitive impairment but did not meet criteria for dementia were classified as having MCI and divided into amnestic (ie, with episodic memory impaired) and nonamnestic subtypes, as previously described.15 Individuals who met these criteria for MCI have been found to have intermediate levels of mortality,14,16 cognitive decline,14,17- 18 and plaques, tangles, and cerebral infarction19 relative to persons without cognitive impairment and dementia. All clinical classification was done blinded to previously collected data.