New criteria and guidelines for the diagnosis of Alzheimer's disease have been published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, marking the first of such updates in 27 years.
Three workgroups, spearheaded by the Alzheimer's Association and the National Institute on Aging of the National Institutes of Health, researched and published the information including ready-to-use clinical diagnostic criteria for Alzheimer's dementia and mild cognitive impairment due to Alzheimer's. In four articles—collectively known as the National Institute on Aging/Alzheimer's Association Diagnostic Guidelines for Alzheimer's Disease—researchers expand the definition of Alzheimer's to include two new phases of the disease: (1) presymptomatic and (2) mildly symptomatic but pre-dementia, along with (3) dementia caused by Alzheimer's.
The addition of new phases reflects current thinking that Alzheimer's begins by creating distinct and measurable changes in the brain years or even decades before memory and thinking symptoms are noticeable.
“The new guidelines reflect today's understanding of how key changes in the brain lead to Alzheimer's disease pathology and how they relate to the clinical signs of mild cognitive impairment and Alzheimer's disease dementia,” said Creighton Phelps, PhD, Program Director of the Alzheimer's Disease Centers Program at the National Institutes of Health. “We are also beginning to be able to detect these changes at a preclinical stage, long before symptoms appear in many people.
“With further research on biomarkers, as set forth in the new guidelines, we may ultimately be able to predict who is at risk for development of mild cognitive impairment and Alzheimer's dementia, and who would benefit most as interventions are developed.”
The articles refer to these three phases of Alzheimer's disease progression over time:
• Preclinical Alzheimer's, or measurable changes in biomarkers (such as brain imaging and spinal fluid chemistry) that indicate the very earliest signs of disease, before outward symptoms are visible.
• Mild cognitive impairment due to Alzheimer's, or mild changes in memory and thinking abilities, enough to be noticed and measured, but not impairment that compromises everyday activities and functioning.
• Dementia due to Alzheimer's, or memory, thinking, and behavioral symptoms that impair a person's ability to function in daily life.
The researchers propose that Alzheimer's begins with a long asymptomatic period during which detrimental changes are progressing in the brain, and individuals with biomarker evidence of these changes are at increased risk for developing cognitive and behavioral impairment and progression to Alzheimer's dementia.
There was a broad consensus within the workgroups that much additional research needs to be done to validate the application of biomarkers as they are proposed in the newly-published articles.