Alzheimer’s disease is a major public health issue because:

  • It affects approximately one million people in France and is the leading cause of dementia;
  • Its prevalence is age-related and steadily increasing; it affects 2 to 4% of the population after 65 years and reaches 15% at 80 years;
  • Its morbidity is significant (loss of autonomy for the patient, suffering for caregivers);
  • Its socio-economic cost is massive (very expensive chronic care at home or in institutions).

The cause of Alzheimer’s disease is not yet identified, but the biological cascade leading to the progressive death of neurons is increasingly well understood.

Risk factors are not fully identified: some are genetic, while others are environmental or lifestyle-related (for example, cerebrovascular risk factors and low educational level).

Three major biological abnormalities characterize the disease:

  1. Abnormal accumulation of beta-amyloid (Aß-42) proteins in extracellular clusters (“amyloid plaques” or “senile plaques”). These are mainly present in the associative cortical areas (prefrontal, parietal, and temporal cortices) and relatively spare the primary visual cortex (occipital lobes) and motor cortex (precentral gyrus).
  2. Abnormal accumulation of abnormally phosphorylated tau protein in neuronal extensions, forming neurofibrillary tangles (NFTs). These NFTs are found in large quantities in the internal temporal regions (especially the hippocampi).
  3. Loss of neurons whose extensions were previously affected by NFTs. When this cell loss is massive, it leads to atrophy of the affected regions.