A report published by researchers at Albert Einstein College of Medicine of Yeshiva University in the August 20 issue of JAMA suggests that measuring how much an individual's performance varies across several neuropsychological tests enhances the accuracy of predicting whether older adults will develop dementia.
Developing strategies to improve the prediction and diagnosis of dementia has critical therapeutic and public health implications. "Typically, when neuropsychological tests are used for diagnostic purposes, an individual's level of performance on specific tests is measured against healthy individuals to determine cognitive impairment," says Dr. Roee Holtzer, assistant professor of neurology and psychology at Einstein and lead author of the study. "However, this approach does not take into account intra-individual variability in cognitive function." Intra-individual variability refers to inconsistency in performance measured in the same person.
Dr. Holtzer and Einstein colleagues evaluated 897 individuals, age 70 or older, who have taken part in The Einstein Aging Study, a longitudinal study of aging and dementia in Bronx, New York. Participants had follow-up visits every 12 to 18 months, during 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 variability across several neuropsychological tests, assessed at the initial study visit, predicted future dementia. "We know that level of performance on tests of memory, attention and executive function predicts dementia. However, this study showed for the first time that the degree of variability in performance across neuropsychological tests, measured within a person, improved the prediction of dementia above and beyond one's level of performance on each test alone," says Dr. Holtzer.
In the follow-up visits, participants underwent extensive neurological and neuropsychological testing to determine whether individuals remained normal or became demented. "Of the 897 participants, there were 61 cases of dementia (6.8 percent) identified during the follow-up period, which, on average, was 3.3 years," says Dr. Holtzer. "This figure is in line with what we'd expect for the incidence of dementia in this population."
The study concluded that within-person variability across these tests predicted the development of dementia independently of how people performed on the tests. The authors recommend that their findings be replicated in different populations before they're applied in a clinical setting.