A simple word-memory test may accurately detect the earliest stages of Alzheimer’s disease (search) and improve treatment of the disease, according to a new study.
Researchers found that by weighting individual performance on a standard 10-word recall test used to diagnose Alzheimer’s disease, they were able to significantly improve the accuracy of the test in detecting mild cognitive impairment (search).
Mild cognitive impairment — subtle but measurable memory problems — is the earliest clinical stage of Alzheimer’s disease and related memory disorders and is typically followed by dementia. People who suffer from mild cognitive impairment have memory problems that are greater than normal for their age but otherwise show no symptoms of dementia.
During this stage, an individual’s most complex abilities may be compromised, but activities of daily living, such as traveling, paying bills, and balancing a checkbook, are unaffected.
Spotting Alzheimer’s disease at this early stage is important because there is an irreversible loss of function for every month that mild to moderate Alzheimer’s disease goes untreated. But detecting mild dementia in its earliest stages is difficult because the person may not show any symptoms, and current methods are often not accurate enough.
Researchers say more than 67 percent of Alzheimer’s disease patients are diagnosed when they already suffer from moderate forms of dementia.
A New Way to Use an Old Test
In the study, which appears in the March 29 issue of the Proceedings of the National Academy of Sciences, researchers looked at adding correspondence analysis to the standard word-memory test that has been used by National Institute of Aging for more than 20 years to improve the detection of mild cognitive impairment. Correspondence analysis is a technique that creates weighted scores from individual performance profiles.
The test consists of a series of memory trials using a 10-word list. The individual is shown the words on the list and then asked to recall them after performing another, unrelated task or after a delay.
Usually the score is calculated by recording the number of words recalled in each of the four trials. But in this study, researchers weighted the scores based on the individual’s performance on the intermediate and delayed recall portion of the tests.
The results showed using these weighted scores increased the sensitivity of the test by 12 percent in detecting mild cognitive impairment. The weighted scores predicted mild cognitive impairment vs. normal functioning in 97 percent of the cases. It was 98 percent accurate in distinguishing between mild cognitive impairment and mild dementia.
Researchers say these results represent the highest degree of accuracy reported for a word-memory test in detecting the earliest stages of Alzheimer’s disease.
Because most other screening tests rely primarily on total scores, they could be improved by incorporating the methods presented here, write researcher William R. Shankle of the University of California, Irvine, and colleagues.
SOURCE: Shankle, W. Proceedings of the National Academy of Sciences, March 21, 2005, online early edition; vol 102: pp 4919-4924.