A new study shows that cognitive tests could now detect early signs of Alzheimer's disease on people before even the symptoms of the disease are not present. The new study also shows that biological changes occurring within the brain could also be a sign of the disease before the symptoms become persistent.
In a study published in Neuropsychology Review titled "Detectable Neuropsychological Differences in Early Preclinical Alzheimer’s Disease: A Meta-Analysis," Duke Han of the University of Southern California, the lead author of the study, suggests that cognitive tests could also be used in detecting early signs of Alzheimer's disease in people without the symptoms of it. Before, doctors observe the biological changes and behaviors occurring in the brain in order to see if a disease is emerging.
"There are new imaging methods that can identify neuropathological brain changes that happen early in the course of the disease but the problem is that they are not widely available, can be invasive and are incredibly expensive so I wanted to see whether the cognitive tests I regularly use as a neuropsychologist relate to these biomarkers," Han said. He also serves as an associate professor of family medicine at the Keck School of Medicine of the University of Southern California.
In observing biological changes to detect early signs of Alzheimer's disease, doctors are looking at the activities of amyloid plaques, which are clusters of protein fragments, along with tangles of a protein known as tau, which forms in the brain and grows in numbers. In an article published in Science Daily, If their activities eventually get in the way of the brain's ability to function, it could be an early sign of the disease.
The study concluded that people who had amyloid plaques had a poor performance on neuropsychological tests of global cognitive function, memory language, and visuospatial ability than those people who did not have amyloid plaques. They also performed worse on processing speed and attention/working memory/executive function, which could be a signal for Alzheimer's disease.
Moreover, the study found that people with tau pathology or neurodegeneration had a poor performance on memory tests than people with amyloid plaques. "The presumption has been that there would be no perceivable difference in how people with preclinical Alzheimer's disease perform on cognitive tests and this study contradicts that presumption," Han said.
Five million people in the US are suffering from Alzheimer's disease and it could even reach up to 16 million by 2050, according to the Alzheimer's Association. Currently, there is no cure for the disease.