Alzheimer's disease (AD), also defined as Alzheimer's, is a chronic neurodegenerative disease that normally begins slowly and worsens over time. It is responsible for 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. Language problems, disorientation (including getting lost easily), mood swings, lack of interest, self-neglect, and behavioural difficulties are all possible symptoms as the disease progresses.
When a person's health deteriorates, they often withdraw from family and society. Bodily functions gradually deteriorate, inevitably leading to death. Although the rate of development varies, the average life expectancy after diagnosis is three to nine years. Alzheimer's disease is a disease whose origin is unknown. Its growth is linked to a number of environmental and genetic risk factors. An allele of Apolipoprotein E is the highest genetic risk factor.