CLINICAL SCIENCE OF DEMENTIA

Clinical Science of Dementia



Clinical Science of Dementia

Causes of Alzheimer's Disease

Scientists have not yet been able to determine exactly why and how Alzheimer's disease develops, but they are learning more about these issues all the time. We do know that the brains of patients with this disease develop deposits of a protein called beta amyloid (these deposits are also known as plaques), and that people also develop disorganized masses of protein fibers within the brain cells known as neurofibrillary tangles. In addition, Alzheimer's disease is associated with the death of nerve cells (neurons) in important parts of the brain. Right now, these changes to the brain can only be seen during autopsy after a patient's death, but researchers are working to develop ways of imaging these brain changes in living patients (Caplan, 2010, 1103-1116).

Risk Factors for Alzheimer's disease

A risk factor is not necessarily the cause of a particular condition, but merely something that helps predict it. Some risk factors can indeed cause a particular illness. As an example, we know that smoking can cause lung cancer. The relationship between other risk factors and specific diseases is more complicated, and in many cases scientists do not know if there is any causal relationship involved or not. They just know that people who have a particular risk factor are for some reason also more likely to get a particular disease (Galvin, 2006, 1605-1611).

Age

The biggest risk factor for Alzheimer's disease is age: the older you are, the more likely you are to develop Alzheimer's disease. As an example, one large study found that among people ages 65 to 69, the estimated annual incidence (number of cases developing per year) of Alzheimer's was less than 1 percent. For those ages 70 to 74, the incidence was 1 percent, and for people ages 75 to 79, 2 percent. Estimated incidence of Alzheimer's rose to more than 3 percent among people ages 80 to 84, and to more than 8 percent among those 85 and over.

Family history

Having a close family member with Alzheimer's disease also increases the chances of developing it yourself. People with a first-degree relative, such as a parent or sibling, with Alzheimer's disease have a 10 to 30 percent chance of developing the disorder. The risk is probably higher if the family member developed Alzheimer's disease at a younger age and lower if the family member did not get Alzheimer's disease until late in life (Sager, 2006, 25-9).

Other

Other factors that are more weakly associated with Alzheimer's disease include a history of head injury with loss of consciousness, a history of depression, and a low level of education. The explanation for these associations is not clear, but may relate to brain reserve.

Certain other medical conditions are also associated with a greater likelihood of developing Alzheimer's, but researchers are still working out these relationships. As an example, there is some suggestion that conditions such as high blood pressure (hypertension), low blood pressure (hypotension), and high cholesterol (hypercholesterolemia) may ...