Despite an extension of the planned duration of inclusion and an enrolled patient number inferior than planned, coordinating investigator considered that it was more reasonable to stop inclusions in order to analyze the data already available

The objective of the study is to highlight a modification of the composition of the intestinal microbiota associated with the diagnosis of Alzheimer's disease and its most unfavorable form, Rapid Cognitive Decline (DCR). This identification could lead to diagnostic strategies based on the analysis of the intestinal microbiome, and preventive and curative treatments, based on the modulation of intestinal microbiota

Inclusion Criteria:

For Alzheimer groups without DCR and Alzheimer with DCR:

• patients between 70 and 90 years old
• with mild to moderate Alzheimer's disease (MMSE> 15/30),
• followed in the CMRR of the University Hospital of Nantes or Angers
• having given their informed consent

For the control group (non-Alzheimer's)

• more patients between 70 and 90 years
• consultant for a subjective memory complaint isolated at the CMRR of Nantes or Angers University Hospital,
• having given their informed consent

Exclusion Criteria:

• Major patients under tutorship, curatorship or safeguard of justice
• Cognitive disorders possibly related to a metabolic or psychiatric cause
• History of prescription of antibiotic treatment in the last month
• History of acute gastrointestinal illness in the last month
• History of hospitalization for an acute medical pathology or for a surgical procedure in the last month