• INCLUSION AND EXCLUSION CRITERIA:

DEMENTIA PATIENTS:

Dementia of the Alzheimer type will be defined by a gradual onset with a continuing cognitive decline not due to other central nervous system conditions that cause progressive deficits in memory. The cognitive decline must include a memory impairment but must also be accompanied by at least one other cognitive disturbance such as aphasia, apraxia, agnosia, or a disturbance in executive functioning. The deficits must cause significant impairments in social or occupational performance and represent a decline in function.

Longitudinal subjects will be excluded from specific aspects of the study if they have contraindications to any of the procedures involved as specified in the Hazards and Precautions section. Furthermore, subjects will be excluded if they are not able or willing to assign durable power of attorney (DPA) to an appropriate person.

MILD COGNITIVE IMPAIRMENT (MCI):

Is defined operationally as evidence of cognitive difficulty, including memory problems which are significant to generate a worry for the individual or surrounding family members but not yet sufficient to elicit the diagnosis of possible Alzheimer's disease when evaluated by a physician. As in the Alzheimer's Disease Cooperative Study, these subjects will have a memory complaint and at least one abnormal memory function, but they will still fall within normal limits globally.

AT RISK INDIVIDUALS:

At risk individuals will be defined by one of the following criteria: (a) having a presumptive diagnosis of AD in one or more of their first-degree relatives; or (b) belonging to a family with a known or presumed genetic mutation for AD; and (c) testing within the normal range on a battery of cognitive tests at the time of baseline evaluation.

NORMAL CONTROLS:

They will not have a positive family history of dementia in their first-degree relatives, and they will test within the normal range on the battery of cognitive tests listed previously.