This project aims to study on one hand the early mitochondrial alterations, common or specific, occurring in peripheral cells of patients with Alzheimer's disease or related dementia and, on the other hand, identify the metabolomic biomarkers that may be at the origin of mitochondrial disturbances associated with the disease. This will be the first study combining functional analyses of mitochondria and exploratory metabolomic assessments in the same cohort at early stages of the disease.

Study will be proposed to the patient of the Nice Memory center who had a lumbar puncture and who agreed on the storage of a sample of their cerebrospinal fluid.

Two groups of patients will be compared: the Alzheimer"s disease patient with positive amyloid on the cerebrospinal fluid and the non Alzheimer patient with negative amyloid on the cerebrospinal fluid.

there will also be a group of healthy volonteer with one blood sample

Blood samples will be collected at inclusion and one year to obtain the mitochondrial metabolomic signature

Inclusion Criteria:

• Neurocognitive disorder with spontaneous complaint or reported for at least 6 months
• Diagnostic process according to current Haute Autorité de Santé (HAS) recommendations.
• cerebrospinal fluid biomarker dosage done within the study center and agreement to bio-collection of residual cerebrospinal fluid
• Patient having agreed to sign the informed consent
• Patient affiliated or beneficiary of a social security scheme

For alzheimer group : diagnosis of Alzheimer's disease according to NIA-AA 2024 criteria (presence of a pathogenic amyloid process in the cerebrospinal fluid)

For non alzheimer group : diagnosis of mild or major neurocognitive disorder according to Manuel diagnostique et statistique des troubles mentaux edition 5 (DSM-V) criteria, not linked to Alzheimer's disease (absence of pathogenic amyloid process in the cerebrospinal fluid)

For healthy volonteers:

• Adult patients
• No history of neurological or psychiatric disorders
• No complaints of memory problems or cognitive impairment
• Mini-Mental State Examination (MMSE) score ≥ 27/30
• Clinical Dementia Rating - Sum of Boxes (CDR-SOB) equal to 0
• Patient affiliated with or covered by a social security scheme

Exclusion Criteria:

- Vulnerable people