Alzheimer's Disease Health Channel

Definition

Alzheimer's disease (AD), one form of dementia, is a progressive, degenerative brain disease. It affects memory, thinking, and behavior.

Memory impairment is a necessary feature for the diagnosis of this or any type of dementia. Change in one of the following areas must also be present: language, decision-making ability, judgment, attention, and other areas of mental function and personality.

The rate of progression is different for each person. If AD develops rapidly, it is likely to continue to progress rapidly. If it has been slow to progress, it will likely continue on a slow course.

Alternative Names

Senile dementia/Alzheimer's type (SDAT)

Causes, incidence, and risk factors

The older you get, the greater your risk of developing AD, although it is not a part of normal aging. Family history is another common risk factor.

In addition to age and family history, risk factors for AD may include:

• Longstanding high blood pressure
• History of head trauma
• High levels of homocysteine (a body chemical that contributes to chronic illnesses such as heart disease, depression, and possibly AD)
• Female gender -- because women usually live longer than men, they are more likely to develop AD

There are two types of AD -- early onset and late onset. In early onset AD, symptoms first appear before age 60. Early onset AD is much less common, accounting for only 5-10% of cases. However, it tends to progress rapidly.

The cause of AD is not entirely known but is thought to include both genetic and environmental factors. A diagnosis of AD is made based on characteristic symptoms and by excluding other causes of dementia.