Objective: We aimed to evaluate semantic memory (SM) performance in isolated/idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) and identify the specific profile of SM deficits based on the presence of mild cognitive impairment (MCI).

Background: IRBD is a parasomnia characterized by abnormal behaviors during REM sleep. iRBD is considered a prodromal stage of synucleinopathies, such as Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Moreover, iRBD patients exhibit declines across multiple cognitive domains (e.g., attention, executive functions, and episodic verbal memory), with approximately one-third meeting the criteria for MCI. Semantic memory (SM), which refers to our ability to store and access general knowledge about the world, has received little attention in iRBD research.

Method: Participants with iRBD (n=107) underwent polysomnography, a neurological examination, and a neuropsychological assessment. MCI was identified according to published criteria for this population¹. Two tasks measuring SM were administered: the POP-10, which evaluates famous person knowledge, and the PUB-12, which assesses non-autobiographical retrograde SM. Performance was compared to published normative data to identify abnormal performance (below 1.5 SD). Non-parametric Mann-Whitney and chi-square tests were conducted to compare patients with MCI to those with normal cognition.

Results: Thirty-nine patients (36%) had MCI. No significant between-group differences were found for age, sex, or education. Across the entire sample, 33% and 28% of patients had impaired performance on the PUB-12 and POP-10, respectively. Between-group comparisons revealed that a higher proportion of patients with MCI had impaired performance compared to those with normal cognition on both SM tasks (POP-10: 43% vs. 19%, p < 0.001; PUB-12: 49% vs. 24%, p < 0.001) (Figure 1). Moreover, patients with MCI performed worse than those with normal cognition on both SM tasks (p = 0.02).

Conclusion: SM impairments are common in iRBD, particularly among patients with concomitant MCI. Further studies are needed to evaluate the predictive value of SM deficits in identifying iRBD patients at risk of developing DLB or PD.

Comparing Semantic Memory in RBD-MCI and RBD-NC

References: 1. Gagnon JF, Vendette M, Postuma RB, et al. Mild cognitive impairment in rapid eye movement sleep behavior disorder and Parkinson’s disease. Ann Neurol. 2009;66(1):39-47. doi:10.1002/ana.21680

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MDS Abstracts - https://www.mdsabstracts.org/abstract/semantic-memory-deficit-as-a-potential-risk-factor-of-dementia-in-isolated-rapid-eye-movement-sleep-behavior-disorder/