Disease Information for Alzheimer's syndrome: Definition

Alzheimer"s Disease; Presenile Dementia; Alzheimer"s disease is a progressive condition of the brain affecting memory, thought and language; The degenerative changes of Alzheimer"s disease lead to patches or plaques in the brain and the entanglement of nerve fibers (neurofibrillary tangles); Memory loss and behavioral changes occur as a result of these changes in brain tissue--------- [NORD 2005]--------- Abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles); Today, these plaques and tangles in the brain are considered signs of AD; Scientists also have found other brain changes in people with AD; Nerve cells die in areas of the brain that are vital to memory and other mental abilities, and connections between nerve cells are disrupted; There also are lower levels of some of the chemicals in the brain that carry messages back and forth between nerve cells; AD may impair thinking and memory by disrupting these messages; Age is the most important known risk factor for AD. The number of people with the disease doubles every 5 years beyond age 65; Family history is another risk factor; Scientists believe that genetics may play a role in many AD cases; For example, early-onset familial AD, a rare form of AD that usually occurs between the ages of 30 and 60, is inherited; The more common form of AD is known as late-onset; It occurs later in life, and no obvious inheritance pattern is seen in most families; However, several risk factor genes may interact with each other and with non-genetic factors to cause the disease; The only risk factor gene identified so far for late-onset AD is a gene that makes one form of a protein called apolipoprotein E (ApoE); Everyone has ApoE, which helps carry cholesterol in the blood; Only about 15 percent of people have the form that increases the risk of AD; It is likely that other genes also may increase the risk of AD or protect against AD, but they remain to be discovered;

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