Results from an extensive new study suggest that early symptoms of Alzheimer’s disease appear up to 18 years before the disease is officially diagnosed.
Researchers publishing in the journal Neurology gave 2,125 people, average age 73, a test of memory and thinking skills every three years for 18 years. All of the participants were either European-American or African-American and none had been diagnosed with Alzheimer’s when the study began.
During the course of the study, 23% of the African-American and 17% of European-American participants developed Alzheimer’s. Those who scored lowest on the memory and thinking tests during the first year of the study were 10 times more likely to develop the disease.
“The changes in thinking and memory that precede obvious symptoms of Alzheimer’s disease begin decades before,” said study author Kumar B. Rajan, PhD, with Rush University Medical Center in Chicago. “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 most telling period of the study was for memory and thinking tests completed between 13 and 18 years before the research ended. Every single unit of lower performance on the test (a unit being a standard drop below the average score) was associated with an 85% greater risk of developing the disease.
According to Rajan, “While that risk is lower than the same one unit lower performance when measured in the year before dementia assessment, the observation that lower test scores 13 to 18 years later indicates how subtle declines in cognitive function affect future risk.”
The results indicate that Alzheimer’s begins taking a toll on thinking abilities well before previously thought. The mental corrosion triggered by the disease would appear to develop decades before full-blown diagnosis, and the focus on preventive treatment should shift to earlier in potential patients’ lives, especially those with a family history of the disease.
“Efforts to successfully prevent the disease may well require a better understanding of these processes near middle age,” Rajan said.
The study was published in the journal Neurology.
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