What causes Alzheimer’s disease and how it is diagnosed?

The causes of Alzheimer’s disease are not known. The “amyloid cascade hypothesis” is the most widely discussed and researched hypothesis about the cause of Alzheimer’s disease. The strongest data supporting the amyloid cascade hypothesis comes from the study of early-onset inherited (genetic) Alzheimer’s disease. Mutations associated with Alzheimer’s disease have been found in about half of the patients with early-onset disease. In all of these patients, the mutation leads to excess production in the brain of a specific form of a small protein fragment called ABeta (Aβ). Many scientists believe that in the majority of sporadic (for example, non-inherited) cases of Alzheimer’s disease (these make up the vast majority of all cases of Alzheimer’s disease) there is too little removal of this Aβ protein rather than too much production. In any case, much of the research in finding ways to prevent or slow down Alzheimer’s disease has focused on ways to decrease the amount of Aβ in the brain.

Diagnosis for Alzheimer’s Disease

No specific blood test or imaging test exists for the diagnosis of Alzheimer’s disease. Alzheimer’s disease is diagnosed when:

  1. A person has sufficient cognitive decline to meet criteria for dementia;
  2. The clinical course is consistent with that of Alzheimer’s disease;
  3. No other brain diseases or other processes are better explanations for the dementia.