FIGURE 4. Comparison of Unstructured and Structured Age Cohortsa.
aThe left panel shows a frequency histogram of baseline ages of 157 patients with Alzheimer’s disease from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), an example of an unstructured multicohort longitudinal design. The right panel shows a frequency histogram for a hypothetical structured multicohort longitudinal design with the same number of subjects and range of baseline ages as ADNI.
