The cause of Alzheimer’s disease is not yet known. The “amyloid cascade hypothesis” is the most widely researched hypothesis about the cause of Alzheimer’s disease. The strongest data that supports 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 of the disease. In all of these patients, the mutation leads to excess production in the brain in a specific form of a small protein fragment called “ABeta (Aβ)”. Many scientists believe that in the majority of sporadic cases of Alzheimer’s disease, too little of this Aβ protein is removed rather than too much production. In any case, much of the research is to find ways to prevent or slow down Alzheimer’s disease which has focused on ways to decrease the amount of Aβ in the brain.

Researchers have discovered changes that take place in the brains of people with Alzheimer’s disease. These include:

1. Lower levels of acetylcholine in certain areas of the brain. Acetylcholine is a chemical messenger in the brain (neurotransmitter) needed for some nerve cells to work properly. Other neurotransmitters are also affected.
2. Senile plaques, are clumps of abnormal nerve cells which surrounds abnormal protein (amyloid) deposits, and neurofibrillary tangles, are clumps of material that disrupt the normal structure of nerve cells. Senile plaques and neurofibrillary tangles is seen during examination of the brain after the person is dead.

These brain changes may lead to memory loss and decline in other mental abilities that occur with Alzheimer’s disease. It is not fully known why these brain changes occur in some people and not in others.

Alzheimer’s disease always gets worse over time, but the course of the disease varies from person to person. Some people may still be able to function relatively well until late in the course of the disease.

Scientists are looking at three areas to find the cause:
Family history
It is found that in some families, there’s a connection between family history and Alzheimer’s disease. While for others, a family history of Alzheimer’s disease puts them at greater risk than someone with no family history. Though research in this area is growing, the relation between heredity and Alzheimer’s disease is still unknown.

The external environment
Researchers think that cause of Alzheimer’s disease may be in outside environment like in water, soil or air.

The internal environment
Alzheimer’s disease may be caused by something within our body. It may be a virus, a chemical imbalance or problem with immune system.

Researchers believe that there’s no single cause of Alzheimer’s disease. Instead, they believe it is caused by a combination of factors. Researchers are working around the country to find out what causes Alzheimer’s and how to prevent it. They also are testing new medications to help people with Alzheimer’s live better lives.