Memory May Decline Rapidly Even in Stage Before Alzheimer's Disease

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Memory and thinking skills may decline rapidly for people who have mild cognitive impairment, which is the stage before Alzheimer's disease when people have mild memory problems but no dementia symptoms, and even more rapidly when dementia begins, which is when Alzheimer's disease is usually diagnosed.

The research is published in the March 23, 2010, print issue of Neurology®, the medical journal of the American Academy of Neurology. (See below)

“These results show that we need to pay attention to this time before Alzheimer’s disease is diagnosed, when people are just starting to have problems forgetting things,” said study author Robert S. Wilson, PhD, of Rush University Medical Center in Chicago.

The study involved 1,158 people living in Chicago with an average age of 79. A total of 149 of the participants had Alzheimer’s disease, 395 had mild cognitive impairment, and 614 had no thinking or memory problems.

Memory and thinking skills tests were given to the participants at the beginning of the study and again every three years. People took part in the study for an average of 5.5 years, and up to 11 years.

The thinking skills of those with mild cognitive impairment declined twice as fast each year as those who had no cognitive problems, while the skills of those with Alzheimer’s disease declined four times as fast as those with no cognitive problems.

At the beginning of the study, scores on a global cognition test ranged from an average of 0.5 for people with no thinking problems to 0.2 for people with mild cognitive impairment to -0.5 for people with Alzheimer’s disease. Scores declined by 0.04 per year for those with no thinking problems, by 0.09 for those with mild cognitive impairment, and by 0.17 for those with Alzheimer’s.

“The changes in rate of decline occur as the brain atrophies due to the disease, first mainly in the hippocampus during the initial symptomatic stage, referred to as mild cognitive impairment, then in the temporal, parietal and frontal cortex during the dementing illness phase of Alzheimer’s disease,” said David S. Knopman, MD, of the Mayo Clinic in Rochester, Minn., and Fellow of the American Academy of Neurology, who wrote an editorial accompanying the article.

The study was supported by the National Institute on Aging and the National Institute of Environmental Health Sciences.



R. S. Wilson, PhD, N. T. Aggarwal, MD, L. L. Barnes, PhD, C. F. Mendes de Leon, PhD, L. E. Hebert, ScD and D. A. Evans, MD. Cognitive decline in incident Alzheimer disease in a community population. Neurology 2010;74:951-955.

Objective: To measure the cognitive consequences of incident Alzheimer disease (AD) in older African American and white subjects.

Methods: Data are from the Chicago Health and Aging Project, a longitudinal cohort study of older white and black persons residing in a geographically defined community. At 3-year intervals, the entire study population completed 4 brief cognitive tests, from which a previously established composite measure of global cognition was derived, and a subset underwent detailed clinical evaluation that supported clinical classification of mild cognitive impairment, dementia, and AD. We used mixed-effects models to examine change in cognitive function following the diagnostic evaluation.

Results: On clinical evaluation, 614 persons were found to have no cognitive impairment, 395 had mild cognitive impairment, and 149 had AD (88.5% mild); 10 persons with other dementias were excluded from analyses. During up to 11 years of observation following the clinical evaluation (mean = 5.5, SD = 2.5), the composite measure of global cognition declined a mean of 0.042 unit per year (SE = 0.008, p < 0.001) in those with no cognitive impairment. In comparison to the no cognitive impairment group, the annual rate of decline was increased more than twofold in mild cognitive impairment (estimate = 0.086, SE = 0.011, p < 0.001) and more than fourfold in AD (estimate = 0.173, SE = 0.020, p < 0.001). Results did not reliably vary by race, sex, or age.

Conclusions: Alzheimer disease has a devastating impact on cognition, even in its prodromal stages, with comparable effects in African American and white persons.

Abbreviations: AD = Alzheimer disease; MCI = mild cognitive impairment.

Address correspondence and reprint requests to Dr. Robert S. Wilson, Rush AD Center, Rush University Medical Center, 600 South Paulina Avenue, Suite 1038, Chicago, IL 60612 rwilson@rush.edu