In a meta-analysis of 31 studies amounting to 1,144 Alzheimer's patients and 6,046 healthy controls, Zakzanis and Boulos looked at both neuropsychological and neuroimaging tests to determine their ability to detect preclinical dementia and/or Alzheimer's disease. They also paired a genetic susceptibility (presence of the ApoE gene) to dementia/Alzheimer's with results on both neuropsychological and neuroanatomic tests again attempting to identify which types of tests would prove most accurate in identifying preclinical disease in patients with the ApoE gene.
Specifically, their findings support the use of the California Verbal Learning Test (long delay recall and percent recall) as the best predictor of Alzheimer's type dementia, with executive function type measures also being predictive but less so than both the long and short delay memory tests.
Changes in the hippocampus were the best volumetric or neuroimaging measure but in general volumetric measures were less sensitive to preclinical stages of the dementia than were the neuropsychological tests.
Ironically, while memory assessments were also more predictive of preclinical Alzheimer's than neuroimaging tests for people with the ApoE gene, the most predictive test for such persons still appears to be an odor identification test.
In presenting their findings, the authors note that decline in memory, especially in verbal episodic memory, can be observed in normal elderly people as well as in elderly with mild cognitive impairments and that most of those people will not become future victims of Alzheimer's. How can we tell the difference between those elderly with normal memory impairments and those with preclinical Alzheimer's? The answer, according to the researchers, lies in the magnitude of the memory deficit. Because their study was a meta-analysis of effect sizes, the results allowed them to compare the size of the difference between normal older adults with normal memory decline and older adults with actual dementia.
Presentation: "A Meta-Analysis of ApoE Genotype and Neuropsychologic and Neuroanatomic Changes in Preclinical Alzheimer's Disease," Konstantine K. Zakzanis, Ph.D., University of Toronto, and Mark I. Boulos, B.Sc., University of Toronto, Session 4140, 10:00 - 11:50 AM, August 25, 2002, McCormick Place, Lakeside Center-Level 4, Meeting Room E451a.
Full text paper available from the APA Public Affairs Office
Author contact: Second author Mark Boulos will be available for interviews. He can be reached before and after the convention at (416) 299-5653 or by email at firstname.lastname@example.org.
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