Use of cognitive tests to detect preclinical Alzheimer’s disease

Written by Amy Bamford

New research from the Keck School of Medicine of the University of Southern California (CA, USA) suggests that neuropsychological tests can detect early pre-clinical Alzheimer’s disease (AD) in older adults. The results from the meta-analysis, published in Neuropsychology Review, show that adults with amyloid plaques and tau pathology performed worse on cognitive tests. These novel findings could open up new avenues for early AD detection and management.
Duke Han, Keck School of Medicine of the University of Southern California, explained: “In the last decade or so, there has been a lot of work on biomarkers for early AD. There are new imaging methods that can identify neuropathological brain changes that happen early on in the course of the disease. The problem is that they are not widely available, can be invasive and are incredibly expensive. I wanted to see whether the cognitive tests I regularly use as a neuropsychologist relate to these biomarkers.”

A meta-analysis of 61 studies was carried out to investigate whether cognitively intact adults over 50 years of age would demonstrate differences in neuropsychological performance by amyloid status. The results showed that older adults who were amyloid positive performed worse in the tests of global cognitive function, memory, language, visuospatial ability, processing speed and attention/working memory/executive function when compared with amyloid negative adults.

The results also showed that cognitively intact adults with neurodegeneration or tau pathology, as well as amyloidosis, performed poorer on the memory tests in comparison to amyloid positive individuals.

“The presumption has been that there would be no perceivable difference in how people with preclinical Alzheimer’s disease perform on cognitive tests. This study contradicts that presumption,” Han said. “Having a baseline measure of cognition before noticing any kind of cognitive change or decline could be incredibly helpful because it’s hard to diagnose early Alzheimer’s disease if you don’t have a frame of reference to compare to.

“If people would consider getting a baseline evaluation by a qualified neuropsychologist at age 50 or 60, then it could be used as a way to track whether someone is experiencing a true decline in cognition in the future.”.

“While there’s no cure for Alzheimer’s disease, the earlier you know that you’re at risk for developing it, the more you can potentially do to help stave off that diagnosis in the future,” Han concluded.

Sources: Han SD, Nguyen C, Nikki H et al. Detectable neuropsychological differences in early preclinical Alzheimer’s disease: a meta-analysis. Neuropsychol. Rev. doi:10.1007/s11065-017-9345-5 (2017) (Epub ahead of print); http://keck.usc.edu/detecting-alzheimers-disease-before-symptoms-emerge/