From article...

"Recent estimates suggest that 5.4 million people in America currently have Alzheimer’s disease and that one in eight older Americans will eventually develop Alzheimer’s disease. As our population continues to age, experts estimate that by 2050, 16 million individuals will have Alzheimer’s disease."

http://www.everydayhealth.com/columns/rhythm-break-cares-dance-and-dementia/shall-we-dance-alzheimers-takes-a-spin-with-ballroom-dancing/