Long before symptoms of Alzheimer’s disease become apparent to patients and their families, biological changes are occurring within the brain. Amyloid plaques, which are clusters of protein fragments, along with tangles of protein known as tau, form in the brain and grow in number, eventually getting in the way of the brain’s ability to function. These biological changes can be detected early in the course of Alzheimer’s disease through positron emission tomography (PET) scan or cerebrospinal fluid analysis. Now, a new study led by Keck Medicine of USC neuropsychologist Duke Han, PhD, associate professor of family medicine (clinical scholar) at the Keck School of Medicine of the University of Southern California suggests that cognitive tests are also able to detect early Alzheimer’s in people without symptoms.
“In the last decade or so, there has been a lot of work on biomarkers for early Alzheimer’s disease,” Han says. “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.”
Putting neuropsychological measures to the test
Han and his colleagues conducted a meta-analysis of 61 studies to explore whether neuropsychological tests can identify early Alzheimer’s disease in adults over 50 with normal cognition. The study, which was published in Neuropsychology Review, found that people who had amyloid plaques performed worse on neuropsychological tests of global cognitive function, memory, language, visuospatial ability, processing speed and attention/working memory/executive function than people who did not have amyloid plaques.
The study also found that people with tau pathology or neurodegeneration performed worse on memory tests than people with amyloid plaques. Amyloid plaques and…