Gut Microbiota and Alzheimer's Diseases

The investigator will perform clinical studies to test a hypothesis that participants who have Alzheimer's disease will have different gut/oral microbiota profile as compared to the participants who do not have Alzheimer's disease. The investigators will also check the microbiome of their partners in this study. The investigators plan to perform the studies in 150 participants in Shanghai Tenth's People's Hospital and also in the houses in Shanghai city. Investigators will also measure the beta-amyloid in the feces of the participants. Finally, the investigators will determine cognitive function in these participants.