Cognitive Tests May Help Detect Early Alzheimer’s in Patients Without Symptoms

A Keck School of Medicine of USC study shows that cognitive tests can detect early Alzheimer’s disease in  older adults who do not present symptoms yet.

The study “Detectable Neuropsychological Differences in Early Preclinical Alzheimer’s Disease: A Meta-Analysis” was published in the journal Neuropsychology Review.

It is estimated that 5 million people in the United States have Alzheimer’s disease, and that number could climb to 16 million by 2050, according to the Alzheimer’s Association.

Long before symptoms arise, amyloid plaques (aggregates of beta-amyloid protein), along with tangles of the tau protein, start to accumulate, interfering with normal function of the brain. These brain changes can be detected through positron emission tomography (PET) scan or cerebrospinal fluid analysis. However, such tests are not generally available, are invasive and extremely expensive.

“In the last decade or so, there has been a lot of work on biomarkers for early Alzheimer’s disease,” Duke Han, PhD, Keck School of Medicine of the University of Southern California neuropsychologist and associate professor of family medicine, said in the press release.

“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,” he added.

Han and his colleagues performed an analysis of 61 studies to investigate if cognitive tests could be used to identify early Alzheimer’s disease in adults older than 50 with normal cognition and its association with these biomarkers. PET scan or cerebrospinal fluid analyses were used to detect amyloid plaques and tau pathology.

The researchers found that patients with amyloid plaques performed worse on these tests of global cognitive function, memory, language, visuospatial ability, processing speed and attention/working memory/executive function than patients without the plaques.

“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.

These findings highlight the value of incorporating cognitive testing into routine and annual checkups for older people. Importantly, these tests would help to diagnose and better manage early Alzheimer’s disease, such as using different medications or strategies early on, and interfering in a positive way in the progression of the disease.

“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 said. “For example, exercise, cognitive activity and social activity have been shown to improve brain health.”