Affiliations: [a] Department of Psychology, University of Utah, Salt Lake City, UT, USA
| [b] Advanced Neurobehavioral Health of Southern California, San Diego, CA, USA
| [c] Department of Neurology, Layton Aging and Alzheimer’s Disease Center, Oregon Health & Science University, Portland, OR, USA
| [d] Department of Neurology, Center for Alzheimer’s Care, Imaging, and Research, University of Utah, Salt Lake City, UT, USA
Correspondence:
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Correspondence to: Kevin Duff, PhD, Department of Neurology, Layton Aging and Alzheimer’s Disease Research Center, Oregon Health & Science University, Portland, OR, USA. E-mail: [email protected].
Abstract: Background:Cognitive change in mild cognitive impairment (MCI), a likely prodrome to Alzheimer’s disease, can be tracked with repeated neuropsychological assessments, but there has been little work quantifying these changes over time. Cognitive change can be statistically examined using standardized regression-based (SRB) formulas, which yield a z-score indicating amount of change compared to a normative group. Objective:To use SRB z-scores to quantify cognitive change in a sample of patients classified as MCI at baseline, and to compare cognitive change in those who remained MCI on follow-up (MCI-Stable) and those who progressed to dementia (MCI-Decline). Methods:Using 283 MCI patients from a cognitive disorders clinic who were re-assessed after approximately one- and one-half years, SRB z-scores were calculated for each test in a comprehensive neuropsychological battery for each participant. Results:There was a significant decline between timepoints across all cognitive tests, with the greatest amount of decline on tests of learning and memory. Group differences were seen on nearly all cognitive tests, with the MCI-Decline group showing more decline (i.e., significantly larger and negative z-scores) than the MCI-Stable participants. Notable cognitive decline was also observed in the MCI-Stable group, with z-scores ranging from –0.01 – –2.24 compared to normative data. Conclusion:This study highlights the amount of cognitive decline that occurs in MCI, including for those who remain “stable” and those who progress to dementia. It also demonstrates the value of the SRB method in more clearly quantifying cognitive decline, which may help identify individuals most vulnerable to MCI progression.
