Information on Alzheimer's Disease

Alzheimer's Disease 

Background

Alzheimer's disease (AD) is a progressive degenerative disease of the brain from which there is no recovery. The disease slowly attacks nerve cells in all parts of the cortex of the brain and some surrounding structures, thereby impairing a person's abilities to govern emotions, recognize errors and patterns, coordinate movement, and remember. Ultimately, a person with AD loses all memory and mental functioning.

Alzheimer’s disease is the most common cause of dementia in people age 65 years and older. Dementia is significant loss of cognitive functions such as memory, judgment, attention, and abstract thinking.

There are three brain abnormalities that are the hallmarks of the Alzheimer’s disease process:

• Plaques. A protein called beta-amyloid accumulates and forms sticky clumps of amyloid plaque between nerve cells (neurons). High levels of beta amyloid as associated with reduced levels of the neurotransmitter acetylcholine. (Neurotransmitters are chemical messengers in the brain.) Acetylcholine is part of the cholinergic system, which is essential for memory and learning and is progressively destroyed in Alzheimer’s disease.
• Tangles. Neurofibrillary tangles are the damaged remains of macrotubules, the support structure that allows the flow of nutrients through the neurons. A key feature of these tangled fibers is an abnormal form of the tau protein, which in its normal version helps maintain healthy neurons.
• Loss of nerve cell connections. The tangles and plaques cause neurons to lose their connection to one another and die off. As the neurons die, brain tissue shrinks (atrophies).

The major areas of the brain have one or more specific functions.

Causes

Scientists do not know what causes Alzheimer’s disease. It may be a combination of various genetic and environmental factors that trigger the process in which brain nerve cells are destroyed.

GENETIC FACTORS

Genetics certainly plays a role in early-onset Alzheimer's, a rare form of the disease that usually runs in families. Scientists are also investigating genetic targets for late-onset Alzheimer's, which is the more common form. At this time, only one gene, apolipoprotein E (ApoE) has been definitively linked to late-onset Alzheimer's disease. However, only a small percentage of people carry the form of ApoE that increases the risk of late-onset Alzheimer's. Other genes or combinations of genes may be involved.

ENVIRONMENTAL FACTORS

Researchers have investigated various environmental factors that may play a role in Alzheimer’s disease or that trigger the disease process in people who have a genetic susceptibility. Some studies have suggested an association between serious head injuries in early adulthood and Alzheimer’s development. Lower educational level, which may decrease mental and activity and neuron stimulation, has also been investigated. To date, there does not appear to be any evidence that infections, metals, or industrial toxins cause Alzheimer’s disease.