research team from Rush University Medical Center in Chicago conducted a study
on 2,125 European-American and African-American individuals in Chicago aged
65 years or above. None of the seniors had clinical Alzheimer's
when they were selected for the research.
The individuals enrolled for the study were given tests every
three years that examined their episodic memory, executive function and global
cognition. Episodic memory refers to memory of certain events experienced by
the person. Executive function refers to the ability to plan and carry out
tasks. Cognition refers to the ability of obtaining information and
About 21% of the participants - about 17% of
European-Americans and 23% of the African-Americans - developed Alzheimer's
disease during the study.
The study found that individuals who got the lowest scores in
episodic memory, executive function, and global cognition over an
18-year-long period were almost 10 times more likely to develop Alzheimer's
disease than those with higher scores.
B Rajan, an Indian origin scientist with Rush University Medical Center in
Chicago explains that the changes in some brain function that precede symptoms
of the mental disease begin decades before.
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," says Kumar.
The exact reason for the apparent link between low test
scores and the onset of Alzheimer's disease is not known. Further studies on
larger groups of patients will probably explain why these individuals are
susceptible to Alzheimer's disease.
"A general current concept is that in development of
Alzheimer's disease, certain physical and biological 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," says
1. Kumar B Ranjan et al. Cognitive impairment 18 years before clinical diagnosis of Alzheimer disease dementia. doi: http://dx.doi.org/10.1212/WNL.0000000000001774 Neurology 10.1212/WNL.0000000000001774