This observational study covered all the 30 provincials/municipals/autonomous in mainland China except Hong Kong and Macau. Tier 3 hospitals, psychiatric hospitals, elderly hospitals, nursing home and communities were randomly selected as research centers, and more than 2500 patients with AD and their caregivers were enrolled at last. The main outcome of this study was assessed not only by the electronic medical system of communities and hospitals, but also by questionnaires. Using a societal prevalence-based gross COI approach to estimated the total yearly costs of AD in China.