Incidence of Alzheimer's Disease is expected to increase as the elderly population grows. Early diagnosis and treatment will be the key to lessening the disease's worst effects, but, how to spot the disease before its symptoms become serious (and harm is already done) is a challenge for health professionals. A new study by psychologists Konstantine K. Zakzanis, Ph.D., and Mark Boulos, B.Sc., of the University of Toronto has determined that the best predictor of future Alzheimer's type dementia is a verbal memory test. Their study is presented at the 110th Annual Convention of the American Psychological Association (APA).
In a review of 31 studies with a total of 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 or 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.
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.