Alzheimer's disease is an irreversible, progressive brain disease that slowly destroys memory and thinking skills, and eventually even the ability to carry out the simplest tasks. In most people with Alzheimer's, symptoms first appear after age 65. Estimates vary, but experts suggest that as many as 5.1 million Americans may have Alzheimer's disease. There is no cure for Alzheimer's disease. Because it is complex, many speculate that it is unlikely that any one intervention will be found to delay, prevent or cure it. This is the reason researchers and clinicians focus on several different aspects, including helping people maintain mental function, managing behavioral symptoms and slowing or delaying the symptoms of disease.