The study of more extensive sized sample collections is of great importance in AD due to the neuropathological (e.g., Braak and Consortium to Establish a Registry for Alzheimer's Disease - CERAD scoring), genetic (e.g., APOE carriers vs. non-carriers), and demographic (e.g., age-at-onset, race, ethnicity, and sex) variability observed across patients with the disease. This evidence concerns the gene APOE and Alzheimer disease.