A simple memory test suggests the cognitive symptoms of Alzheimer's disease may appear up to 18 years before an actual diagnosis—six to eight years earlier than previous research had indicated, according to a new study published in the journal Neurology.
For the study, researchers from Rush University Medical Center administered a memory and thinking test to 2,125 Chicago residents every three years for 18 years. At the start of the study, the average age of participants was 73, and none had been diagnosed with Alzheimer's.
Over the course of the study, 21% of participants were diagnosed with Alzheimer's disease.
Why are women far more likely to have Alzheimer's?
Overall, those with the lowest cognitive test scores during the study's first year were 10 times more likely than those with the highest scores to be diagnosed with Alzheimer's over the course of the study. And among tests completed 13 to 18 years before the end of the study, every one unit drop in test performance corresponded with an 85% increase in participants' risk of developing the disease.
The results only show a link between cognitive test scores and broad risk on the group level, and the researchers "cannot currently detect such [risk] changes in individuals" using the test, says study co-author Kumar Rajan.
But the data show that the "changes in thinking and memory that precede obvious symptoms of Alzheimer's disease begin decades before" it is diagnosed—and that there may be a longer window of time when physicians could take steps to forestall the most debilitating effects of Alzheimer's, Rajan explains.
Rajan adds that "efforts to successfully prevent the disease may well require a better understanding" of the features of Alzheimer's that develop near middle age, since researchers believe that "certain physical and biologic changes precede memory and thinking impairment" among those that develop the condition (Eunjung Cha, "To Your Health, Washington Post, 6/29; Feller, UPI, 6/29; Dallas, HealthDay/CBS News, 6/26; Park, TIME, 6/24; American Academy of Neurology release,6/24; Rajan et al., Neurology, 6/24).
On delivering effective Alzheimer's care:
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