Cognitive impairment no dementia - neuropsychological and neuroimaging characterization of an amnestic subgroup

Abstract

Background/aims: Cognitive impairment no dementia (CIND) describes individuals whose cognitive functioning falls below normal but who do not meet dementia criteria. An important goal within CIND is to identify subgroups that will predictably progress to Alzheimer disease. CIND with amnestic deficits has been associated with high risk of Alzheimer disease but has until now been investigated on a retrospective basis. In this study a prospectively defined amnestic CIND group was characterized on a detailed neuropsychological test battery and on structural magnetic resonance imaging (MRI) measures.

Methods: Amnestic CIND was defined as meeting at least 1 but not all DSM-IV-TR criteria for dementia, scoring > or =1 SD below norms on Rey Auditory Verbal Learning Test delayed recall, having a Clinical Dementia Rating score of 0.5 and a Mini-Mental State Exam score > or =24. This cross-sectional study compared subjects meeting these criteria (n = 25) to age- and education-matched controls (n = 26). The neuropsychological battery included memory and nonmemory measures that were analyzed as continuous variables and dichotomized into impaired (> or =1 SD below controls) versus nonimpaired. MRI scans were evaluated with a global-brain volumetric measure [brain fractional ratio (BFR)] and with visually based medial temporal lobe atrophy (MTA) ratings.

Results: Amnestic CIND had neuropsychological impairment in the episodic memory domain and also in nonmemory domains. There were 80% of CIND subjects with multidomain impairment. The most clear-cut nonmemory impairment was in the verbal ability domain, with 64% of subjects affected and a moderate effect size (d = 0.7). On MRI, BFR was lower (74.5 +/- 4.6 vs. 75.5 +/- 4.4) and MTA higher (72 vs. 38% with MTA > or =1) in CIND than in control subjects. BFR correlated with MTA (r = -0.45) and with a composite memory score (r = 0.296).

Conclusion: A prospective amnestic CIND grouping appears to identify individuals with a multidomain pattern of neuropsychological impairment and with both medial temporal lobe and global brain atrophy.