Alzheimer’s is a chronic neurodegenerative disease that usually starts slowly and gradually worsens over time. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As the disease advances symptoms can include problems with language, disorientation, mood swings, loss of motivation, not managing self-care and behavioural issues. As a 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 typical life expectancy following diagnosis is three to nine years.