One of the most common forms of dementia, a neurologic disease characterised by the loss of mental ability severe enough to interfere with normal activities of daily living. Named after German psychiatrist and neuropathologist Alois Alzheimer who first described it in 1906, Alzheimer's disease is a incurable, degenerative, and terminal condition. It usually occurs in old age, and is marked by a decline in cognitive functions such as remembering, reasoning, and planning.