Alzheimer disease (AD), the most common form of dementia in the elderly, is rapidly becoming a major health problem in developed countries where the number of elderly people continuously grows due to improved medical care. Consequently, the number of AD patients is increasing and thus far no effective therapies are available. Clinically the disease can be diagnosed with 90% reliability on the basis of neurological examination, neuropsychological testing and brain imaging techniques. A definite diagnosis, however, requires the post-mortem detection of senile plaques (SPs) and neurofibrillary tangles (NFTs) in the brain. The SPs are extracellular deposits mainly composed of amyloid P (Ap) surrounded by dystrophic neurites. NFT are intraneural inclusions of paired helical filaments composed of hyperphosphorylated tau.

Although age is the major risk factor for AD, population survey and family studies have provided substantial evidence that genetic factors are major contributors to the expression of AD.