A preliminary report published in the August 20 issue of JAMA suggests that within-person variability on neuropsychological testing may be associated with development of dementia in older adults.
"Developing strategies to improve the prediction and diagnoses of dementia has paramount therapeutic and public health implications," the authors write. "When neuropsychological tests are used for diagnostic purposes, an individual's level of performance on specific tests is measured against healthy normative samples to determine cognitive impairment. However, this approach does not take into account intra-individual variability in cognitive function." Intra-individual variability is inconsistency in cognitive performance within a person.
Roee Holtzer, Ph.D., and colleagues from the Albert Einstein College of Medicine, Yeshiva University, New York, evaluated 897 individuals, age 70 or older, who are part of The Einstein Aging Study, a longitudinal study of aging and dementia in Bronx County, New York. Participants had follow-up visits every 12 to 18 months, at which they underwent detailed neurological and neuropsychological evaluations. The researchers included tests for verbal IQ, attention/executive function, and memory. The study focused on whether within-person across-neuropsychological test variability predicts future dementia.
"Of the 897 participants, there were 61 cases of incident dementia (6.8 percent) … identified during the follow-up period (mean [average] 3.3 years)," the authors report. "On the basis of the consensus clinical diagnostic procedures, 47 participants developed incident dementia of the Alzheimer type and 18 participants developed incident vascular dementia. During the study, 128 individuals died, as expected for the age of this cohort. Of these, 18 had developed incident dementia."
"In summary, within-person across-neuropsychological test variability was associated with development of dementia independently of performance of the neuropsychological tests. This finding needs to be replicated in different populations before it is applied in a clinical setting," the authors conclude.
- Roee Holtzer; Joe Verghese; Cuiling Wang; Charles B. Hall; Richard B. Lipton. Within-Person Across-Neuropsychological Test Variability and Incident Dementia. JAMA, 2008; 300 (7): 823-830 [link]
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