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.

This study is a population-based cohort study. Oldest-old people (aged 80 and over) will be enrolled.

Data collection Social economics information include: name, gender, age, nationality, marital status, personal habits, occupation, level of education, family living situation, monthly income, way to go to a doctor and medical payment, etc The health status and disease will be obtained by review the medical records as well as the narration of the subjects and their family members. We will focus on diseases with high disability mortality, high social burden. Multiple indicators or abilities will be evaluated through the scale, including life or acting ability, nutritional status, cognitive ability, psychological status, social support, quality of life self-assessment, etc., so as to comprehensively understand the comprehensive information of the participants.

Basic physical examination and special clinical examination will be performed to obtain multiple objective indicators reflecting the subject's physical function The basic health examination includes; Blood pressure, respiration, heart rate, pulse; Height, weight, waist circumference, hip circumference, arm circumference, calf circumference, grip strength, vital capacity, tooth condition, hearing condition, visual acuity, ECG, etc.

Special examinations include the blood, urine, and stool specimens. Imageological examination like MRI, fundus photography, and optical coherence tomography will also be conducted.

Inclusion Criteria:

• All the people aged 80 years and above in the target community in Beijing

Exclusion Criteria:

• People who were hospitalized for long period (6 months or more) or at the end of their lives were excluded.

All the people aged 80 years and above in the target community in Beijing will be enrolled, and people who were hospitalized for long period (6 months or more) or at the end of their lives were excluded.