Alzheimer's disease (AD) is a neurodegenerative disease that usually starts slowly and progressively worsens,[2] and is the cause of 60¨C70% of cases of dementia.[2][15] The most common early symptom is difficulty in remembering recent events.[1] As the disease advances, symptoms can include problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, self-neglect, and behavioral issues.[2] As a person's condition declines, they often withdraw from family and society.[16] Gradually, bodily functions are lost, ultimately leading to death. Although the speed of progression can vary, the average life expectancy following diagnosis is three to twelve years.[11][12][13]

Reference
Wiki: Sporadic alzheimer disease