Clinical aspects of Alzheimer's disease.

Alzheimer's disease (AD) is the most common of the dementing disorders. AD begins insidiously and progresses gradually; it is characterized clinically not only by an impairment in cognition, but also by a decline in global function, a deterioration in the ability to perform activities of daily living, and the appearance of behavioral disturbances. No definitive tests for the diagnosis are available, and AD is a diagnosis of inclusion based on patient history, physical examination, neuropsychological testing, and laboratory studies. Disease progression is highly variable, and median survival after the onset of dementia ranges from 5 to 9.3 years. Early recognition of AD allows time to plan for the future, and to treat patients before marked deterioration occurs.