Alzheimer's disease (AD) is a progressive, neurodegenerative disease characterized by memory loss, language deterioration, impaired visuospatial skills, poor judgment, indifferent attitude, but preserved motor function. AD usually begins after age 65, however, its onset may occur as early as age 40, appearing first as memory decline and, over several years, destroying cognition, personality, and ability to function. Confusion and restlessness may also occur. The type, severity, sequence, and progression of mental changes vary widely. The early symptoms of AD, which include forgetfulness and loss of concentration, can be missed easily because they resemble natural signs of aging. Similar symptoms can also result from fatigue, grief, depression, illness, vision or hearing loss, the use of alcohol or certain medications, or simply the burden of too many details to remember at once.

There is no cure for AD and no confirmed way to slow the progression of the disease. For some people in the early or middle stages of the disease, conventional medication may alleviate some cognitive symptoms. Some medications may help control behavioral symptoms such as sleeplessness, agitation, wandering, anxiety, and depression.
AD is a progressive disease and the course of the disease varies from person to person. Some people have the disease only for the last 5 years of life, while others may have it for as many as 20 years. The most common cause of death in AD patients is infection.

The Lancet Publishing Group (July 12, 2007) proposes that to meet the new criteria for probable AD, patients must show progressive memory loss over more than six months, plus at least one or more of the supportive biomarker criteria. These include: atrophy in a particular part of the brain shown by MRI, abnormal biomarker proteins in the cerebrospinal fluid, a specific pattern on PET of the brain, and a genetic mutation for AD within the immediate family. The authors say: "These new criteria are centred on a clinical core of early and significant episodic memory impairment…the timeliness of these criteria is highlighted by the many drugs in development that are directed at changing pathogenesis."

The researchers add that validation studies are required to advance the new criteria and optimise their sensitivity, specificity and accuracy. They conclude: "When effective disease-modifying medications are available, the argument for such biologically based studies will be even more compelling.

"These proposed criteria move away from the traditional two-step approach of first identifying dementia according to degree of functional disability, and then specifying its cause. Rather, they aim to define the clinical, biochemical, structural, and metabolic presence of AD." In an accompanying comment, Dr Norman Foster, Center for Alzheimer's Care, Department of Neurology, University of Utah, USA says: "We should seize this opportunity to reopen the discussion of Alzheimer's disease diagnosis. The time is right to use the advanced technology at our disposal to improve the early, accurate diagnosis of dementia and develop more effective treatments."