Researchers are rapidly learning more about the chemical changes that damage brain cells in Alzheimer's disease. Apart from the few with familial Alzheimer's disease, it is not known why some people develop Alzheimer's disease and others do not. It is likely that a number of factors contribute to development of the disease, including environmental, genetic and health factors.
Alzheimer's disease is characterised by specific changes in the brain that include the formation of amyloid plaques (fibrous patches) and neurofibrillary tangles (strands of proteins). An abnormal build-up of a protein called beta-amyloid causes amyloid plaques to form outside the brain cells. Inside the brain cells, another protein called tau builds up and causes neurofibrillary tangles.
These protein accumulations disrupt messages within the brain because they damage connections between brain cells. The brain cells eventually die and brain volume shrinks. These brain changes occur gradually and actually begin many years (on average around 15 years) before the symptoms of Alzheimer's disease occur. The brain is able to compensate for the early damage, but eventually the damage becomes too great and brain function is affected.