A diagnosis of dementia can be frightening for those affected by the syndrome, their family members, and caretakers. Alzheimer's disease (AD) is the most common form of dementia in those over the age of 65. As many as 5 million Americans age 65 and older may have AD, and that number is expected to double for every 5-year interval beyond age 65. But Alzheimer's is only one of many dementia disorders; another 1.8 million people in the U.S. have some other form of dementia. Among all people with dementia, many are believed to have a mixed type of dementia that can involve more than one of the disorders. This book provides a general overview of various types of dementia, describes how the disorders are diagnosed and treated, and offers highlights of research that is supported by the National Institute of Neurological Disorders and Stroke and the National Institute on Aging, both part of the National Institutes of Health (NIH).