VOA常速英语2008年-Exercise Shown to Prevent Alzheimer's Disease

The World Health Organization estimates there are about 18 million people with Alzheimer's disease.  And that figure is expected to double by the year 2025.  Many of those Alzheimer's patients will live in developing countries.  New U.S. figures estimate that one out of every eight Americans will also develop the disease.  But as VOA's Melinda Smith reports, there is ample evidence that something can be done about it now.