Development and validation of the Memory Performance Index: reducing measurement error in recall tests

Area of Science:

• Neuroscience
• Cognitive Psychology
• Gerontology

Background:

• The Memory Performance Index (MPI) is a novel metric derived from the Consortium to Establish a Registry for Alzheimer's Disease Wordlist (CWL).
• MPI quantifies word recall patterns on a 0-100 scale, demonstrating high accuracy (96-97%) in differentiating normal cognition from mild cognitive impairment.

Purpose of the Study:

• To evaluate the MPI's performance in a large, diverse population.
• To assess the relationship between MPI scores and cognitive decline across different dementia severities.
• To compare the explanatory power of MPI with traditional wordlist recall scores.

Main Methods:

• 121,481 individuals (ages 18-106) were assessed using the CWL, with MPI and recall scores analyzed against demographic and administration variables.
• Predictor effect sizes (Cohen's f(2)) were calculated for MPI, immediate free recall (IFR), delayed free recall (DFR), and total free recall (TFR).
• In a separate cohort (N=441), MPI scores were analyzed across Functional Assessment Staging Test (FAST) stages.

Main Results:

• MPI explained 55.0% of the variance, significantly more than IFR (24.9%), DFR (23.4%), and TFR (26.9%).
• Age had a large effect on MPI but a small effect on other recall measures.
• MPI scores showed a significant progressive decline across all dementia severity stages (FAST stages 1-6).

Conclusions:

• MPI scores decrease with increasing dementia severity, validating its use as a measure of cognitive decline.
• MPI demonstrates superior ability to explain variance compared to traditional total recall scores.
• The enhanced explanatory power of MPI suggests improved sensitivity for detecting treatment effects in clinical trials.