New Alzheimer's guidelines redefine stages, set biomarkers for future research

New guidelines on Alzheimer's disease describe new stages, including a pre-clinical stage, and suggest new biomarkers for research purposes.

The National Institute on Aging and the Alzheimer's Association issued three papers that update the last set of guidelines from 1984. The new guidelines were published online and will appear in the May issue of Alzheimer's and Dementia: The Journal of the Alzheimer's Association:

• “Introduction to the Recommendations from the National Institute on Aging and the Alzheimer's Association Workgroups on Diagnostic Guidelines for Alzheimer's Disease.” “
• “The Diagnosis of Mild Cognitive Impairment Due to Alzheimer's Disease: Recommendations from the National Institute on Aging and Alzheimer's Association Workgroup.”
• “The Diagnosis of Dementia Due to Alzheimer's Disease: Recommendations from the National Institute on Aging and the Alzheimer's Association Workgroup.”

Three stages identified by the new criteria are pre-clinical Alzheimer's disease, mild cognitive impairment due to Alzheimer's disease, and dementia due to Alzheimer's disease. Pre-clinical Alzheimer's disease is marked by measurable changes in biomarkers that indicate the earliest signs of disease, before symptoms such as memory loss and confusion about time or place are noticeable. While the criteria and guidelines identify this as a stage of Alzheimer's disease, they do not establish diagnostic criteria. Rather, they propose additional research into what tests might confirm that a person is in this or another stage of the disease, such as brain imaging strategies and spinal fluid proteins.

The definition of mild cognitive impairment due to Alzheimer's disease includes mild changes in memory and thinking that are noticeable to the person and to family members and friends and that can be measured, but that do not affect daily function. The guidelines define four levels of certainty for ruling out other causes and arriving at a diagnosis of mild cognitive impairment due to Alzheimer's disease. Markers of this stage include beta-amyloid accumulation in the brain and biomarkers showing that nerve cells in the brain are injured or actually degenerating.

Dementia due to Alzheimer's disease includes memory, thinking and behavioral symptoms that impair a person's ability to function in daily life, the workgroup concluded. The workgroup stressed that its recommendations on pre-clinical Alzheimer's disease currently have no clinical utility and are intended only for research purposes.