As per a new study, errors on memory and thinking tests may signal Alzheimer's up to 18 years before the disease can be diagnosed.
Rush University Medical Center's Kumar B. Rajan said that the changes in thinking and memory that precede obvious symptoms of Alzheimer's disease begin decades before.
He added that while scientists cannot currently detect such changes in individuals at risk, they were able to observe them among a group of individuals who eventually developed dementia due to Alzheimer's.
Based on tests completed 13 to 18 years before the final assessments took place, one unit lower in performance of the standardized cognitive test score was associated with an 85 percent greater risk (relative risk of 1.85) of future dementia.
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, noted Rajan.
Rajan added that a general current concept is that in development of Alzheimer's disease, certain physical and biologic changes precede memory and thinking impairment. 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, he concluded.
The study appears online in Neurology.
