Cognitive test recommended as part of routine screening

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 through positron emission tomography (PET) scan or cerebrospinal fluid analysis.
Now, a new study led by Keck Medicine of USC neuropsychologist Duke Han, suggests that cognitive tests can also detect early Alzheimer’s in people without symptoms.
Han says new imaging methods can identify neuropathological brain changes that happen early, but they are not widely available, can be invasive and are "incredibly expensive."
Han and his colleagues analyzed 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,and 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 tau pathology were confirmed by PET scan or cerebrospinal fluid analysis.
“The presumption has been that there would be no perceivable difference in how people with preclinical Alzheimer’s disease perform on cognitive tests," he said. "This study contradicts that presumption."
Han believes cognitive testing should be included in annual checkups for older people.
“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,” Han said. “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.”
Early detection could be a powerful tool, Han said.
“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,” he said. “For example, exercise, cognitive activity and social activity have been shown to improve brain health.”
An estimated 5 million people in the United States have Alzheimer’s, and that number could reach 16 million by 2050, according to the Alzheimer’s Association.
Source: Keck School of Medicine of the University of Southern California