REM sleep behavior disorder and dementia - Cognitive differences when compared with AD

Objective: To determine whether the dementia associated with REM sleep beha vior disorder (RBD) differs from Alzheimer's disease (AD) and, if so, wheth er differences in cognitive performance between RBD/dementia and AD resembl e reported differences between dementia with Lewy bodies (DLB) and AD. Meth ods: This retrospective study compares neurocognitive performance between 3 1 patients with degenerative dementia and polysomnography-confirmed RBD and 31 patients without brainstem Lewy body pathology who met Consortium to Es tablish a Registry for Alzheimer's Disease (CERAD) clinical and neuropathol ogic criteria for AD. The patient groups did not differ in dementia severit y (based on Global Deterioration Scale score) or duration. Results: RBD pre ceded or coincided with the onset of cognitive decline in 94% of the patien ts. All but one patient with RBD/dementia bad one or more of the following clinical features of DLB: visual hallucinations, extrapyramidal signs, or f luctuating cognition/alertness. The data revealed significantly worse perfo rmance on attention, perceptual organization, visual memory, and letter flu ency for the RBD/dementia group, whereas the AD group showed significantly worse performance on confrontation naming and verbal memory. Conclusions: P atients with RBD and degenerative dementia demonstrate a significantly diff erent pattern of cognitive performance from patients with AD. Most of the p atients in the RBD/dementia sample also meet criteria for possible or proba ble DLB, and the pattern of cognitive differences from AD is similar to rep orted comparisons between DLB and AD. The cognitive and clinical data provi de evidence to suggest that the dementia associated with RBD may represent DLB.