A study of mental decline in the years prior to diagnosis of Alzheimer’s disease suggests that changing the focus of testing may allow physicians to detect signs of the disease three years earlier.
Current cognitive testing typically focuses on episodic memory, or the ability to remember things such as word lists or information from a reading. But School of Medicine scientists found that another class of mental abilities known as visuospatial skills begins to deteriorate up to three years prior to diagnosis. These skills are tested with tasks such as connecting the dots or using a guide to build a structure with blocks.
“We may need to rethink what we look for as the earliest signs of mental change associated with Alzheimer’s disease,” said senior author James Galvin, M.D., associate professor of neurology, of neurobiology and of psychiatry. “If we can better recognize the first signs of disease, we can start treating patients earlier, and, hopefully with new treatments, we can slow or perhaps even stop their progress into dementia.”
The results were published in the October issue of Archives of Neurology.
Galvin and his co-authors analyzed long-term data from volunteers at the Memory and Aging Project at the University’s Alzheimer’s Disease Research Center (ADRC). For three decades, researchers have been regularly conducting extensive testing of volunteers to uncover the factors associated with the normal, healthy retention of mental function in seniors. The new study analyzes data on 444 volunteers ages 60-101 that were gathered between 1979-2006.
Scientists categorized cognitive testing results into a global measure of cognitive abilities as well as three specific types of mental skills: episodic memory, visuospatial skills and working memory, which assesses the ability to manipulate facts from memory, such as repeating a list of numbers backward.
Declines in episodic memory and working memory became discernible a year before volunteers were diagnosed with Alzheimer’s disease. Losses in the composite assessment of cognitive abilities were detectable two years prior to diagnosis, and visuospatial skills began to decay three years earlier. Galvin said the losses in visuospatial skills were particularly noticeable if testing tasks were timed.
Researchers also analyzed the data using a new model that not only tracks the speed of decline in a mental ability but also the acceleration of the decline. Episodic memory’s decline accelerated more slowly than that of both visuospatial skills and working memory, which declined fastest.
The new perspective may allow doctors to detect signs of Alzheimer’s earlier, but more information will be needed to make a firm diagnosis. To make that possible, researchers at the ADRC are trying to take what they’ve learned in the new study and correlate it with biomarkers, which are physical changes associated with preclinical Alzheimer’s disease. These include such tests as scanning the brain for amyloid plaques or analyzing the levels of proteins in the cerebrospinal fluid.
Amyloid brain plaques, a primary characteristic of Alzheimer’s disease, can begin building in patients 10 years or more before clinical symptoms become apparent, Galvin said.