Detecting Alzheimer’s Disease 20 Years Before Symptoms Appear

Posted by Christian Elliott - 17th July 2012

A research team at Washington University School of Medicine just published the results of a study that looked at a number of cognitive changes and biomarkers that can be used to predict the risk of Alzheimer’s Disease long before symptoms appear – in some cases up to 20 years before symptom onset.

The study, published this month in the New England Journal of Medicine, has some unusual characteristics compared to the typical research project on Alzheimer’s. First, the average age of study participants is 39 years, far younger than other studies. Second, about 70% of the 128 participants have a strong genetic predisposition to a form of dementia called Familial Alzheimer’s Disease, or FAD. FAD is also sometimes referred to as early-onset (before age 65) Alzheimer’s.

The participants who were gene carriers for the early-onset form of Alzheimer’s allowed the researchers to observe a “fast forward” view of the disease progression, and compare them to the non-carriers in the study.

What they found was that there were several tests that can reliably give a caution flag many years before Alzheimer’s symptoms appear. The tests fall into three main categories:

Cerebrospinal fluid (CSF) tests require a lumbar puncture, and measure the levels of certain brain proteins that are known to change during Alzheimer’s Disease progression. MRI and PET imaging scans can detect changes (shrinkage) and protein deposits in brain structures, and also measure glucose consumption in the brain, which declines in Alzheimer’s patients. Memory and cognitive tests measure a variety of memory, logic, and reasoning skills.

Moving Research Tools into the Doctor’s Office

This study provides some very useful information, but the gap between research tools and “routine” doctor’s office screening tests is still very large. Consider the following test features with cost:

    Cerebrospinal Fluid (CSF) Tests: Invasive procedure, expensive test ( $2,000+ with diagnostic services)

    Brain Imaging (MRI,PET) Tests: Non-invasive procedure, very expensive test ($3,000 – $6,000)

    Memory/Cognitive Tests: Non-invasive procedure, less expensive test ($150 – $500 in office)

Given the test costs alone, it’s clear that memory screening is the best choice for a general purpose test. Episodic (short term) memory impairment is one of the clearest signs of possible Alzheimer’s. A number of paper tests do a decent job with cognitive screening, but newer computerized/tablet/online cognitive tests tend to be more sensitive and precise vs paper screening for memory impairment.

With the new Medicare Annual Wellness Visit now in its second year, this preventive health visit might be able to serve as a platform for routine cognitive health screening for older adults.