The aim of the study is 1) to search new biomarkers and develop clinically applicable early diagnosis and prediction methods of Alzheimer's disease, and 2) to investigate how the proposed lifetime risk and protective factors for Alzheimer's disease contribute to pathological hallmarks of AD or other brain changes in living human through annual comprehensive clinical and neuropsychological evaluation and biannual brain imaging (MRI and MRA, Fluorodeoxyglucose(FDG)-PET, Pittsburgh compound B (PiB)-PET), AV--1451 PET, and body specimen (blood, gene, and hair) analysis.