The project of Bio-AD is a population- based cohort study among the elderly in China. The project includes not only Alzheimer's disease (AD including familial AD and sporadic AD), but also other clinical stage of AD, as well as elderly people with normal cognitive function. The project will collect, detect and screen the special biomarkers at different clinical stage of AD based on body fluid, gene and brain image. The standard and consistent assessment protocols are employed to obtain clinical, cognitive, genetic, neuroimaging and biospecimen data. The purpose of this project is to establish a panel of biomarkers which could be used to diagnose AD at the early stage, and to establish a risk prediction models for AD to predict the 5-years risk of the onset and progression of AD among elderly population in China.