Alzheimer's disease (AD), one form of
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
More than 4 million Americans currently have AD. 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.
Prior theories regarding the accumulation of aluminum, lead, mercury, and other substances in the brain leading to AD have been disproved. The only way to know for certain that someone had AD is by microscopic examination of a sample of brain tissue after death.
The brain tissue shows "neurofibrillary tangles" (twisted fragments of protein within nerve cells that clog up the cell), "neuritic plaques" (abnormal clusters of dead and dying nerve cells, other brain cells, and protein), and "senile plaques" (areas where products of dying nerve cells have accumulated around protein). Although these changes occur to some extent in all brains with age, there are many more of them in the brains of people with AD.
