Alzheimer's disease (AD), is the most common form of Dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death. Most often, AD is diagnosed in people over 65 years of age, although the less-prevalent early-onset Alzheimer's can occur in much younger people. In 2006, there were 26.6 million people worldwide with AD. Alzheimer's is predicted to affect 1 in 85 individuals globally by 2050. The most common early symptom is short term memory loss—difficulty in remembering recent events. The diagnosis is usually confirmed with tests that evaluate behavior and thinking abilities, often followed by a brain scan. As the disease advances, symptoms can include confusion, irritability, aggression, mood swings, trouble with language, and long-term memory loss. As the person's condition declines they often withdraw from family and society. Gradually, bodily functions are lost, ultimately leading to death. Although the speed of progression can vary, the average life expectancy following diagnosis is approximately seven years. Fewer than 3% of individuals live more than 14 years after diagnosis. Alzheimer's disease is known for placing a great burden on caregivers; the pressures can be wide-ranging, involving social, psychological, physical, and economic elements of the caregiver's life. In developed countries, AD is one of the most costly diseases to society.