MINNEAPOLIS, June 29 (UPI) -- Errors in memory and thinking on tests may show the potential to develop Alzheimer's disease up to 18 years before symptoms are visible and it can be diagnosed.
An 18-year study found that one unit lower in score on the test 13 to 18 years before the final assessment of participants was associated with 85 percent greater chance of developing Alzheimer's, researchers said.
"A general current concept is that in development of Alzheimer's disease, certain physical and biologic changes precede memory and thinking impairment," said Kumar B. Rajan, Ph.D., an assistant professor at Rush University Medical Center in Chicago, in a press release. "If this is so, then these underlying processes may have a very long duration. Efforts to successfully prevent the disease may well require a better understanding of these processes near middle age."
Every 3 years for 18 years,2,125 Chicago residents with an average age of 73 tests were given memory and thinking tests. None of the participants had the disease at the beginning of the study.
During the study, 23 percent of African-Americans and 17 percent of European-Americans developed Alzheimer's.
Participants with lower test scores during the first year of the study were found to be 10 times more likely to be diagnosed with Alzheimer's, and the odds increased by 10 for each unit that scores were lower than average.
"The changes in thinking and memory that precede obvious symptoms of Alzheimer's disease begin decades before," Rajan said. "While we cannot currently detect such changes in individuals at risk, we were able to observe them among a group of individuals who eventually developed dementia due to Alzheimer's."
The study is published in Neurology.