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.

Studies have shown that gut/oral microbiome and beta-amyloid in body may have a significant impact on the behavior and brain pathology consistent with Alzheimer's disease (AD) neuropathogenesis. The objective of this study is to assess whether the gut/oral microbiome and feces beta-amyloid of AD patients are different from those of the participants without AD and their partners. The investigators plan to recruit 150 subjects, including three groups of normal elders, AD patients and the partners of the AD patients. The cognitive function will be assessed and the feces and oral samples will be collected to determine whether there are differences or correlations.

Inclusion Criteria:

• aged 60 and older

Exclusion Criteria:

• with other acute gastrointestinal diseases
• with other severe neuropsychiatric disorders

Elderly participants with normal congition will be collected from community. Alzheimer's disease participants and their spouse will be collected from Shanghai Tenth People's Hopital.