For the first time in 27 years, new criteria and guidelines for the diagnosis of Alzheimer’s disease have been published by three expert workgroups spearheaded by the Alzheimer’s Association and the National Institute on Aging (NIA) of the National Institutes of Health (NIH). If you have been diagnosed with Alzheimer’s or have a loved one with the disease, you may be asking, what does this mean for me?
In the short term, the new guidelines probably won’t affect how you and your loved ones interact with your doctor regarding the disease. For example, there are no new tests that you should be asking for at this time. However, this is a landmark event for the field. We believe this moves us significantly closer to our goal of eventually detecting and treating Alzheimer’s disease before people experience the devastating symptoms of loss of memory and thinking abilities.
Here’s how: An overarching goal of Alzheimer’s doctors and researchers, the Alzheimer’s Association, and the NIA is to enable people to live long, healthy lives free of the disability caused by Alzheimer’s. There is consensus that treating the disease before symptoms occur is how this goal will be met. However, no generally accepted way exists to identify Alzheimer’s at its presymptomatic — and potentially most treatable — stage. The new guidelines address this in two notable ways.
1. New Stages of the Disease Defined
First, the new guidelines 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. This reflects current thinking that Alzheimer’s begins creating distinct and measurable changes in the brains of affected people years, perhaps decades, before memory and thinking symptoms are noticeable.
According to the authors of the new diagnostic guidelines, in order to facilitate the possibility of future presymptomatic treatment of Alzheimer’s, it was important to define the disease from the earliest changes in the brain, not only the observable, symptomatic stages of the disease.
The new guidelines also update current criteria for diagnosing dementia caused by Alzheimer’s disease and mild cognitive impairment (MCI). People with MCI experience a decline in memory, reasoning or visual perception that’s measurable and noticeable to themselves or to others, but not severe enough to be diagnosed as Alzheimer’s or another dementia.
2. Biomarkers for Earlier Detection and Greater Diagnostic Accuracy
The new guidelines also establish a framework and a research agenda for using biomarkers (substances that reflect biological changes in the brain associated with Alzheimer’s) to improve the accuracy of diagnosis of all three stages of the disease. A biomarker is a naturally occurring, measurable substance or condition in the body that reliably indicates the presence or absence of disease or the risk of later developing a disease; for example, blood glucose levels are a biomarker of diabetes, and cholesterol levels are a biomarker of cardiovascular disease risk.
Doctors will not diagnose the new presymptomatic phase of Alzheimer’s until further research identifies the most reliable biomarkers indicating that Alzheimer’s is beginning to develop. Once reliable biomarkers are confirmed, they will also be used to more accurately distinguish “MCI due to Alzheimer’s disease” from MCI due to other causes. They will also be used to increase the accuracy of diagnosing dementia due to Alzheimer’s.
Results of both fluid (e.g., cerebrospinal fluid and blood) and brain imaging (e.g., magnetic resonance imaging and positron emission tomography) tests are being studied as possible biomarkers for Alzheimer’s. Two biomarker categories are identified in the criteria and guidelines: (1) biomarkers showing the level of beta-amyloid accumulation in the brain and (2) biomarkers showing that nerve cells in the brain are injured or actually degenerating.
Much additional research needs to be done to validate the application of biomarkers as they are proposed in the newly published criteria and guidelines. These studies are likely to take at least decade to accomplish. This highlights the need for a greater commitment to research, including increasing funding for Alzheimer’s research and recruiting more volunteers for Alzheimer’s clinical trials.