Objective: To determine whether psychometric, mood and behavior, or electrophysiologic modalities can predict the advent of mild cognitive impairment (MCI) in a longitudinally studied, normal aged population.
Design: Cohorts of healthy, normal aged subjects are stratified into two groups: (1) subjects who are free of subjective complaints of cognitive impairment (Global Deterioration Scale [GDS] stage 1); and (2) subjects with subjective complaints of impairment who are free of clinically manifest deficits (GDS stage 2). These cohorts are studied at baseline and followed to assess outcome.
Materials and Methods: Baseline evaluations included:(1) a combinatorial psychometric variable, the psychometric deterioration score (PDS) (Reisberg et. al., Drug Development Research, 1988); (2) Hamilton depression scale (Hamilton, Journal of Neurology, Neurosurgery and Psychiatry, 1960) total scores and individual items; (3) Quantitative EEG (QEEG) variables (John et. al., Science, 1988), and (4) demographic variables. The behavioral and QEEG variables were examined in separate analyses.
Results: In the behavioral measures analyses, a sample of 453 subjects with a GDS stage of 1 or 2 at baseline, seen between 1984 and 1997, was examined. Of these, 179 were at GDS stage 1 at baseline and 274 were at GDS stage 2 at baseline. Only 9 of the 179 GDS stage 1 subjects had MCI or dementia at follow-up (5.0%). In contrast, 112 of 197 normal aged subjects with a baseline GDS stage of 2 who were successfully followed (from the original GDS stage 2 cohort of 274 subjects), had MCI or dementia at follow-up (56.9%). Therefore, an analysis was done of the variables predicting decline to MCI or dementia in the normal aged, subjectively impaired subjects (GDS stage 2). In these GDS stage 2 subjects, the psychometric PDS scores and Hamilton depression total scores were among the variables which significantly predicted subsequent decline. In a second analysis, QEEG variables were examined in normal GDS stage 2 subjects followed for > 7.0 years. Of 44 subjects who remained alive and were followed, 17 remained normal (38.6%) and 27 declined to MCI or dementia (61.4%). In a logistic regression analysis, selected QEEG variables predicted decline with a predictor accuracy of 90%.
Conclusion: These results indicate that the presence or absence of subjective complaints significantly predicts decline to MCI or dementia in normal, healthy, aged persons. Furthermore, in aged subjects with subjective complaints who are normal, psychometric scores, Hamilton depression scores, and electrophysiologic measures are significant predictors of decline. These findings add to previous findings of the accuracy of imaging predictors in these subjects (de Leon, et. al., Proceedings of the National Academy of Sciences, (USA), 2001).
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