Understanding Alzheimer's is not an easy task. It is a very complex disease, which is quite similar to a jigsaw puzzle. Many individual pieces of the puzzle have been identified. Many pieces of the puzzle remain yet to be discovered.
Alzheimer's disease is a progressive degeneration of brain cells that is more commonly present as people age. Its frequency of appearance grows very rapidly after the age of 65. By the time we are 85, approximately 50 percent of people are suffering from Alzheimer's disease itself. Alzheimer's disease is therefore the most common form of dementia. Memory, mental focus, comprehension and other higher cognitive functions are affected. Alzheimer's disease does not represent a consequence of normal aging; it represents a disease process that is more common in the elderly.
It has been known for somewhat over 100 years that there are two varieties of protein fragments which accumulate in the brain of patients who developed Alzheimer's disease. The first is beta-amyloid which results in the development of beta-amyloid plaques. We have now developed research scans, which can identify beta-amyloid plaques in the brain in patients with Alzheimer's disease, as well as those individuals suspected as having early Alzheimer's disease. The second is Tau protein, which results in the development of brain "tangles", which are seen under the microscope. Early research is underway to develop PET scans (similar to a CAT scan with injective) which can identify Tau protein accumulation in individuals suspected of having early Alzheimer's disease. These two substances, beta-amyloid and Tau, likely are involved in the brain injury which results in the clinical expression of Alzheimer's disease. However, there are still many unanswered questions.
Additionally, there is a variety of lipoprotein, a protein which transports fat molecules (such as cholesterol in the body), which has a genetic variability and one of its forms, which is genetically transmitted, does increase the risk of developing Alzheimer's disease. This increased risk does not necessarily suggest that patients with this form (ApoE4) will get Alzheimer's disease, but clearly it raises the risk that a person with this genotype has greater risk. It has been long noted that people with parents who are affected by Alzheimer's disease appear to be at higher risk of developing the condition themselves.