Normative Values for Cognitive Testing and Alzheimer's Imaging Biomarkers in Young Adults

Biomarkers of Alzheimer's disease (AD) occupy an essential place in recently formulated
diagnostic criteria for AD where their role is to identify the pathophysiological processes
underlying cognitive impairment or to predict time to dementia. Three of these biomarkers
are brain imaging tests (amyloid PET, FDG PET, and structural MRI). In order to effectively
use AD biomarkers for diagnostic and prognostic purposes, continuous values much be divided
into normal and abnormal ranges. This requires that a cut point(s) be established in the
continuous distribution of values for each biomarker.

The investigators objective in this proposal is to obtain imaging biomarker data in a group
of individuals who are appropriate for establishing normative values for AD biomarkers. The
investigators believe the most valid approach to establishing biomarker cut points is to
base them on the upper bound of the range observed in young to early-middle-age subjects in
whom the presence of occult AD pathology is extremely unlikely. Based on a large volume of
community-based autopsy data, that upper age limit would be about 50 years old. The lower
age bound for a group of subjects used to establish normative AD biomarker values would have
to be based on considerations of brain maturation, which may continue into the middle- to
late-20s. Thus, taking the above into consideration, the ideal age range for establishing
normative AD imaging biomarker data (amyloid PET, FDG PET, and structural MRI) may be ages
30-49 years old.