英语流行话题听力:Unit 35 关于阿尔茨海默氏病

Unit 35
　　About Alzheimer's Disease
　　Dementia is a brain disorder that seriously affects a person's ability to carry out daily activities. The most common form of dementia among older people is Alzheimer's disease (AD), which involves the parts of the brain that control thought, memory, and language. Scientists think that as many as 4.5 million Americans suffer from AD. The disease usually begins after age 60, and risk goes up with age.
　　AD is named after Dr. Alois Alzheimer, a German doctor. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. He found abnormal clumps. 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.
　　Scientists do not yet fully understand what causes AD. Age is the most important known risk factor for AD. Family history is another risk factor. Scientists believe that genetics may play a role in many AD cases. Scientists still need to learn more about what causes AD. In addition to genetics, they are studying education, diet, and environment to learn what role they might play in the development of this disease.
　　AD begins slowly. At first, the only symptom may be mild forgetfulness. In this stage, people may have trouble remembering recent events, activities, or the names of familiar people or things. They may not be able to solve simple math problems. Such difficulties may be a bother, but usually they are not serious enough to cause alarm.
　　However, as the disease goes on, symptoms are more easily noticed. People in the middle stages of AD may forget how to do simple tasks, like brushing their teeth or combing their hair. They can no longer think clearly. They begin to ae problems speaking, understanding, reading, or writing. Later on, people with AD may become anxious or aggressive, or wander away from home. Eventually, patients need total care.
　　AD is a slow disease, starting with mild memory problems and ending with severe brain damage. No treatment can stop AD. However, for some people in the early and middle stages of the disease, some dugs may help prevent some symptoms from becoming worse for a limited time. Developing new treatments for AD is an active area of research. Research has shown that vitamin E, estrogen, and ginkgo biloba slow the progress of AD.