Enhancing detection of those at-risk for dementia: a revised classification procedure for mild cognitive impairment

Date

2009-05-29T18:08:05Z

Authors

Vanderhill, Susan Diane

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Abstract

Evidence for the utility of the Mild Cognitive Impairment (MCI) classification as a predictor of impending dementia in older adults is somewhat limited. Although individuals with MCI show elevated rates of conversion to dementia at the group level, heterogeneity of outcomes is common at the individual level. Using data from a prospective five-year longitudinal investigation of cognitive change in a sample of 262 healthy older adults aged 64 to 92 years, this study was designed to address key limitations in current MCI classification procedures which tend to rely on single occasion assessment (Traditional MCI) by evaluating an alternate operational definition of MCI requiring evidence of persistent cognitive impairment over multiple testing sessions (Persistent MCI), and four subsequent variations of this operational definition. It was hypothesized that: (1) prevalence of Traditional MCI would exceed prevalence of Persistent MCI across all variations in the operational definition, (2a) both the Traditional MCI and Persistent MCI groups would show lower levels of performance and greater decline in both cognitive and functional status over five years relative to Controls, (2b) the magnitude of these differences between those classified as Persistent MCI and Controls would exceed the magnitude of differences between those classified as Traditional MCI and Controls, and (3) the pattern of findings outlined in hypothesis 2 would persist under the four variations of the Traditional MCI and Persistent MCI inclusion criteria. Results were consistent with Hypothesis 1, and partially consistent with Hypotheses 2 and 3. In general, the Persistent MCI groups showed a lower mean baseline level of performance and a steeper trajectory of cognitive decline compared to the Control group and the Traditional MCI groups, although the sample-wide change in cognitive and functional status was small. There was some evidence that the variation of Persistent MCI classification which specified persistent memory impairment as an inclusion criteria achieved optimal prediction of cognitive and functional decline. Results are discussed with reference to retest effects, cognitive reserve, and clinical utility of the Persistent MCI concept for enhancing prediction of dementia in older adults.

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Keywords

Mild Cognitive Impairment, Dementia, Neuropsychology, Cognitive Aging, Psychometrics

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