Dementia is a brain disorder that seriously affects a person's ability to carry out daily activities. The most common form of dementia among older people is Alzheimer's disease (AD), which involves the parts of the brain that control thought, memory, and language. Age is the most important known risk factor for AD. The number of people with the disease doubles every 5 years beyond age 65. AD is a slow disease, starting with mild memory problems and ending with severe brain damage. The course the disease takes and how fast changes occur vary from person to person. On average, AD patients live from 8 to 10 years after they are diagnosed, though the disease can last for as many as 20 years. Current research is aimed at understanding why AD occurs and who is at greatest risk of developing it, improving the accuracy of diagnosis and the ability to identify those at risk, discovering, developing, and testing new treatments, and discovering treatments for behavioural problems in patients with AD. This book presents important research in the field from around the world.