For the first time in 27 years, clinical diagnostic criteria for Alzheimer's disease dementia have been revised, and research guidelines updated. They mark a major change in how experts think about and study Alzheimer's disease.

The updated guidelines now cover three distinct stages of Alzheimer's disease:

• Preclinical – is currently relevant only for research. It describes the use of biomarkers that may precede the development of Alzheimer’s.
• Mild Cognitive Impairment– Current biomarkers include elevated levels of tau or decreased levels of beta-amyloid in the cerebrospinal fluid, reduced glucose uptake in the brain, and atrophy of certain brain regions. Primarily for researchers, these may be used in specialized clinical settings.
• Alzheimer's Dementia – Criteria outline ways clinicians should approach evaluating causes and progression of cognitive decline, and expand the concept of Alzheimer's dementia beyond memory loss to other aspects of cognition, such as word-finding, vision/spatial issues, and impaired reasoning or judgment.

The criteria are available at http://www.alzheimersanddementia.org/content/ncg