Alzheimer's disease is a progressive and fatal brain disease affecting about 5.3 million people in the U.S. That number is expected to grow to as many as 16 million by 2050, according to the the association's 2009 Alzheimer's Disease Facts & Figures report. The disease causes memory loss as it destroys brain cells and accounts for 50% to 70% of all dementia cases. There is no cure for Alzheimer's, although symptoms can be treated to lessen its affects. Six of 10 with Alzheimer's will wander away at some point, according to the Alzheimer's Association.