For many years, doctors have been working hard to determine what causes Alzheimer's disease. Due to the complex nature of the disease, the exact causes are not yet fully understood. However, strides are being made on a daily basis, and researchers have a much clearer picture of Alzheimer's than they did even a few years ago.

Most people with Alzheimer's disease have large quantities of plaques and tangles built up in their brain. Plaques are deposits of the protein beta-amyloid accumulating in the spaces between the brain's nerve cells. Tangles are deposits of the protein tau that accumulate and become twisted inside of the brain's nerve cells

Two Types of Alzheimer's Disease

Researchers have determined that there are two types of Alzheimer's: Familial Alzheimer's disease and Sporadic Alzheimer's disease.

Familial Alzheimer's is a rare form of the disease. It is characterized by an early onset and affects less than 10% of Alzheimer's patients.

People with Familial Alzheimer's have a ?deterministic gene? which inevitably leads to the development of the disease. Only a few hundred families in the world have been found to carry the deterministic gene for Alzheimer's.

Sporadic Alzheimer's is the more common form of the disease. There is no deterministic gene present in Sporadic Alzheimer's patients. The onset of the disease is much later in life (usually after age 65).

Although there is no specific gene linked to this form of the disease, genetic factors do appear to play a role in its development.

6 Risk Factors to Know Right Now

Doctors have identified several risk factors which they can link to the development of Alzheimer's. The following 6 factors have shown to be prominent causes of the disease:

1. Age ? Alzheimer's disease usually develops after age 65. Less than 5% of people age 65-74 have Alzheimer's, but the chance of developing the disease doubles every 5 years after age 65. Almost 50% of the population over 85 is at risk for Alzheimer's.

2. Family History ? Your chances of developing Alzheimer's are up to 7 times greater if you have a first degree relative (parent, sibling) that has the disease. This number is even higher if multiple family members have the disease.

3. Genetics ? The APOE-e4 gene has been identified as a risk gene for Alzheimer's. A risk gene increases the likelihood of developing a disease, but unlike a deterministic gene, it fortunately doesn't guarantee you will develop it.

The APOE gene provides the blueprint for one of the proteins that carries cholesterol in the blood stream. Everyone inherits a copy of an APOE gene from each parent. There are three types of APOE genes: APOE-e2, APOE-e3, and APOE-e4. Only the APOE-e4 gene has been linked to Alzheimer's. People with one copy of the APOE-e4 gene are 2-3 times more likely to develop Alzheimer's. People with two copies of the gene (approximately 1% of the population) have a 9 times greater risk.

4. Gender ? Women have a greater risk of developing Alzheimer's than men.

5. Education ? Several studies have shown a connection between less education and an increased risk of Alzheimer's. However, more research is needed in this area.

6. Head Injuries ? Serious traumatic head injuries, such as concussions, have been linked to an increased risk of Alzheimer's.

But there is good news. According to Dharma Singh Khalsa, M.D., President and Medical Director of the non-profit Alzheimer's Research and Prevention Foundation, many of these risk factors can be controlled by adopting good lifestyle choices.

Dr. Khalsa has found that by lowering stress, maintaining a healthy diet, and staying physically and mentally active, it is possible to dramatically reduce your risk of developing Alzheimer's.

So while we are still uncertain as to precisely what causes Alzheimer's disease, it is clear that we have considerable power to lower our chances of developing it ? if we take good care of our body and mind.