Objective: To investigate the cognitive decline in dementia with Lewy bodies (DLBs) and characterize the contribution of Lewy bodies (LBs) to cognitive impairment in the presence of concurrent Alzheimer disease (AD).
Methods: Cognitive deficits and rates of progression attributable to DLB and AD neuropathology were investigated in three groups of participants from the longitudinal cohort of the Alzheimer Disease Research Center at Washington University with autopsy-confirmed diagnoses of pure DLB (n = 9), mixed DLB/AD (n = 57), and pure AD (n = 66). Factor analysis was used to recover latent constructs in a comprehensive psychometric test battery, analysis of variance was used to test group differences on the observed dimensions, and random effects models were used to test longitudinal rates of cognitive decline.
Results: Patients with AD pathology performed worse on the verbal memory dimension. Patients with LB pathology performed worse on the visuospatial dimension. Combined pathology affected visuospatial performance but not verbal memory. The rate of cognitive decline in the DLB, DLB/AD combined, and the pure AD groups was equivalent.
Conclusions: The comorbid presence of DLB and AD alters the cognitive presentation of visuospatial deficits in dementia but does not alter dementia progression. Both visuospatial and verbal abilities declined at similar rates across the three patient groups. DLB diagnosis may be improved, particularly when there is comorbid AD, by using domain-specific testing.