Rudolph C. Hatfield, PhD., edited by Kathryn Patricelli, MA
Researchers continue to investigate risk factors that may increase the chance that a person will develop Alzheimer's disease. A risk factor is some condition that can raise the probability that a person will develop a disease or disorder. However, just having the risk factor alone will not guarantee that the person will develop a specific disease or disorder. People who have more than one risk factor have an even higher chance that they will develop the disease or the disorder in question. Many risk factors associated with developing Alzheimer's disease have been identified. The major risk factors that appear to increase the chances that one may develop Alzheimer's disease include:
Age: The research has indicated that as people get older the chance that they will develop Alzheimer's disease begins to increase dramatically. Starting at age 65 people begin to develop an increased risk for Alzheimer's disease. For every five years after the age of 65 (e.g., 70, 75, 80, etc.) the risk nearly doubles. However, simply getting older does not mean that a person is destined to develop Alzheimer's disease.
Family History: People who have a relative that has been diagnosed with Alzheimer's disease also have an increased risk to develop the disorder themselves. The risk for Alzheimer's disease increases for people who have first-degree relatives (parents, brothers, and/or sisters) who are diagnosed with Alzheimer's disease. The chance is lower for people who have more distant relatives ( uncles, aunts, cousins, etc.) who have been diagnosed with the disorder. If a person has more than one relative diagnosed with Alzheimer's disease, then their risk to develop the disorder is increased even further. This risk factor is often considered to be a sign of some type of genetic cause or contribution, but it can also be the result of environmental factors.
Gender: Women appear to develop Alzheimer's disease at higher rates than men do. This risk factor is complicated by the fact that women still tend to live longer than men. So, age may also contribute to the findings of higher rates of Alzheimer's disease in women.
A History of Head Injury: Research has found a connection between people who have experienced major head injuries and then later develop Alzheimer's disease. It is not fully understood how these factors are related. It is believed that the type of brain damage that occurs in people who experience a major head injury somehow promotes the slow and progressive deterioration in the brain that happens in Alzheimer's disease.
Down Syndrome: People with Down syndrome, a genetic factor that is a major cause of intellectual disabilities, very often develop Alzheimer's disease at an early age (often in their late 30s or early 40s). Researchers are not sure why this happens, but suspect that it is due to genetic factors.
Cardiovascular Factors or Heart Health: Researchers have also found that there is a connection between heart health factors and developing Alzheimer's Disease and other forms of dementia. These factors include high levels of cholesterol, high blood pressure, or even diabetes. The heart is responsible for pumping blood and delivering nutrients and oxygen to organs in the body. Researchers believe that conditions that decrease the ability of the heart to perform its functions are related to the development of brain disorders such as dementia.
Much of the research that investigates the risk factors to developing Alzheimer's disease looks at genetic contributions to the disorder. Researchers divide the genes that can increase the risk to develop Alzheimer's disease into 2 types.
Risk Genes (Susceptibility Genes): People who have these genes have an increased chance that they may develop Alzheimer's disease. However, simply having the gene does not guarantee that the person will develop Alzheimer's disease. The best known of these genes is the APOE-e4 gene that is located on chromosome 19.
Deterministic Genes: The presence of deterministic genes is very rare. People who inherit deterministic genes will develop Alzheimer's disease, often at an early age. These genes are associated with the Familial Type of Alzheimer's disease that runs in families, develops early, and progresses very rapidly. Unless a person has a very strong family history of Alzheimer's disease the likelihood of having one of these genes is extremely small (only about 1% of all people diagnosed with Alzheimer's disease inherit these genes). The deterministic genes currently identified are Amyloid precursor protein (APP, which is located on chromosome 21), Presenilin-1 (PS-1, which is located on chromosome 14), and Presenilin-2 (PS-2, which is located on chromosome 1).
Except for the presence of deterministic genes, researchers believe that genes and lifestyle factors interact to increase a person's risk to develop any type of disease or disorder, including Alzheimer's disease. People cannot control their heredity or the fact that they will age over time, but they can control how they live. One way to reduce the chance that one will develop Alzheimer's disease is to eat healthy and get plenty of exercise. Researchers have found that people who stay physically and mentally active and eat a healthy diet have a decreased risk to develop Alzheimer's disease.