Scientists from Washington University in St. Louis have developed an approach to estimating when a person who is likely to develop Alzheimer’s disease, but has no cognitive symptoms, will start showing signs of Alzheimer’s dementia.
The research is published in Neurology and was conducted by Suzanne Schindler et al.
The algorithm uses data from a kind of brain scan known as amyloid positron emission tomography (PET) to gauge brain levels of the key Alzheimer’s protein amyloid beta.
In those who eventually develop Alzheimer’s dementia, amyloid silently builds up in the brain for up to two decades before the first signs of confusion and forgetfulness appear.
Amyloid PET scans already are used widely in Alzheimer’s research, and this algorithm represents a new way of analyzing such scans to approximate when symptoms will arise.
Using a person’s age and data from a single amyloid PET scan, the algorithm yields an estimate of how far a person has progressed toward dementia—and how much time is left before cognitive impairment sets in.
In the study, the team analyzed amyloid PET scans from 236 people. The participants were an average of 67 years old at the beginning of the study.
The researchers also accessed over 1,300 clinical assessments on 180 of the participants. The assessments typically were performed every one to three years.
Most participants were cognitively normal at the start of data collection, so the repeated assessments allowed the researchers to pinpoint when each participant’s cognitive skills began to slip.
The team found eople in the study who reached the tipping point at younger ages took longer to develop cognitive symptoms than those who reached it later in life.
Participants who hit the tipping point at age 50 typically took nearly 20 years to develop symptoms; those who hit it at age 80 took less than 10 years.
The power of this new technique is that it requires just one brain scan, plus the person’s age.
With that data, the model can estimate the time to symptom onset, plus or minus several years.
In this study, the correlation between the expected age of symptom onset and the true age at diagnosis was better than 0.9 on a scale of 0 (no correlation) to 1 (perfect correlation).
After age, the genetic variant APOE4 is the strongest risk factor for Alzheimer’s dementia.
People who carry one copy of the variant are two to three times more likely to develop Alzheimer’s dementia than the general population, and people who carry two copies are 10 times more likely.
In this study, people with the high-risk variant hit the tipping point younger, but once that point was passed, they followed the same trajectory as everyone else.
At an out-of-pocket cost of about $6,000, amyloid PET brain scans are too expensive for routine clinical use. However, this algorithm could help accelerate the pace of drug development by streamlining clinical trials.
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If you care about dementia risk, please read studies about antibiotic drug that may effectively treat common dementia, and new stem cell therapy to treat dementia.
For more information about brain health, please see recent studies about eye problems linked to a higher risk of dementia, and results showing common high blood pressure drugs may prevent Parkinson’s, dementia.
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