Cognitive Test Score Dispersion VS. Traditional Memory Composite Scores: Predicting Mild Cognitive Impairment (MCI) & Dementia among Cognitively Impaired, Not MCI Patients

Abstract Objective To compare mild cognitive impairment (MCI) and dementia conversion rates between global neuropsychological dispersion (GD) and traditional memory neuropsychological composite score (MComp) in participants with baseline evidence of cognitive decline but no diagnosis of MCI or dementia. Methods Data from the National Alzheimer’s Coordinating Center (NACC) for 364 participants with a CDR of 0.5, no initial diagnosis of MCI or dementia, and five visits were analyzed. GD was the intraindividual standard deviation across baseline normative (NACC norms) neuropsychological performance. MComp was the mean of the four verbal and visual memory normed scores. Multinomial logistic regression models fit statistics compared GD and MComp as predictors of conversion to MCI/dementia, adjusting for age, sex, race, ethnicity, ApoE4 status, and stratified by suspected etiology (Alzheimer’s disease [ad] or no-ad). Lower Akaike Information Criteria (AIC) values indicate better model fit and predictions. Results 37% progressed to MCI, and 47% to dementia by visit 5. 53% of these were suspected to have ad etiology, and 47% non-ad. MComp showed a better fit with significant predictions of MCI and dementia progression in both suspected ad (AIC: 351.77, p < 0.001) or non-ad etiology (AIC: 215.02, p < 0.004), versus GD was only significant for non-ad etiology (AIC: 385.74, p < 0.003). Better memory performance predicted a lower likelihood of conversion to non-ad MCI (B = -0.65, p = 0.003) and non-ad dementia (B = -1.33, p < 0.001). GD predicted eventual progression to non-ad dementia (B = 2.311, p = 0.004), but not non-ad MCI. Conclusion Traditional memory composite score may be a better predictor of MCI and dementia conversion than cognitive dispersion in individuals with early cognitive decline who do not yet meet MCI criteria.