It is not. Healthy people can remain intellectually active and alert throughout their lives, experiencing little more than a slight drop in mental agility as they age. Cause Doctors still do not know what causes Alzheimer's disease. Whatever the cause or causes, Alzheimer's disease characteristically brings with it certain microscopic changes in brain tissue. For example, nerve endings are damaged and link together to form plaques.
Nerve cells show deformations called neurofibrillary tangles.
Brain chemistry also changes. Alzheimer's patients have too little acetylcholine, a neurotransmitter linked to memory, and higher than normal amounts of aluminium in the brain, among other abnormalities. Researchers are investigating genetic factors because some families have more cases than would normally be expected. But the incidence increases among older age groups. Overall, Alzheimer's is believed to be the leading cause of senile dementia - the loss of mental and physical functions in older people.