VOA常速英语:Five New Genes Associated with Risk of Alzheimer's

Countries around the world are anticipating a wave of new cases of Alzheimer's disease and a host of new families that will have to cope with the toll of this incurable, brain-wasting disease. That's because people are living long enough to get late-onset Alzheimer's. But science is offering a glimmer of hope. Two large studies of Alzheimer's patients provide important new genetic clues about who is at risk for getting the disease.

Scientists in the U.S. and Europe have been conducting an intensive search for the genetic triggers for Alzheimer's. Their studies confirmed five genes already known to be associated with it, and now they've come up with five more.

"These findings, the 10 genes - either singly or additively - combine to increase the risk of Alzheimer's disease;  [They] certainly speak to the point that there is a genetic, a very strong genetic component to the disease," said Dr. Steven Snyder, who is a neuroscientist at the U.S. National Institutes of Health, which provided funding for the U.S. study.

Scientists say for late-onset Alzheimer's, a disease that strikes people aged 65 and older, up to 80 percent of the cases can be explained by genetic variations. Dr. Snyder says many more genes may be involved, but with the findings of these studies, researchers hope to develop drug therapies to help delay or prevent the disease. Some scientists estimate it will be at least 15 years before drugs could be developed to combat Alzheimer's or genes could be manipulated to reduce the risk.

"Manipulation will come in time," Dr. Snyder said.  "Unfortunately, it will be too much time. For science to progress, it has to be slow and methodical."

Dr. Snyder points out that genetic makeup does not always dictate a person's risk of getting Alzheimer's.

"It won't explain 100 percent of an individual's risk of Alzheimer's disease," he said. "There are other aspects of biology and epigenetics that will account for some of the differences. And the epigenetic differences can be positive and negative."  

Epigenetics are something that affects a person without changing genetic makeup, such as lifestyle choices.

For example, studies show people who speak more than one language don't develop recognizable symptoms of Alzheimer's until five years later than those who speak only one language. Another study finds that exercise both delays the onset of Alzheimer's symptoms and improves mental ability.  Likewise, there have been indications that high cholesterol, stroke and head injuries can increase the risk of developing the disease. 

At present, there is no proven way to prevent Alzheimer's disease, and the numbers of people who get it are expected to multiply rapidly.  Alzheimer's Disease International predicts that the number of cases will almost double every 20 years, so that by 2030, 66 million people will have it and by 2050, 115 million people and their families will be affected by this devastating disease. That's why public health officials and medical scientists are so focused on finding a way to slow the onset of Alzheimer's or find a way to prevent it.