This study aims to investigate the health status of the oldest-old population and to explore the key factors associated with their quality of life The study will select all the elderly aged 85 years and above from Lanqiying Community, Qinghuayuan Street, Haidian District, Beijing, and enroll them after informed consent. Demographic, sociological, economic, physiological information and disease-related records will be collected through questionnaire interviews, scales, and examinations. After the first survey, the participants will be followed for 2 years to collect information about deaths or major health events. The baseline survey will be re-conducted two years later.