Objective: This study aims to investigate the cognitive profile in people with REM-sleep behavior disorder (RBD) and hyposmia, in a prodromal Parkinson’s disease (PD) cohort.

Background: RBD is a parasomnia, characterized by excessive muscle tone and abnormal behaviors during the REM-sleep stages. RBD and olfactory dysfunction are considered as risk factors for synucleinopathies, such as PD [1]. Other non-motor symptoms like cognitive changes are part of the prodromal stages of PD. Knowledge of these alterations in prodromal PD is still limited [2].

Method: A total of 82 participants from the Luxembourgish RBD study and its control cohort have been included in the study. All participants were assigned to the pRBD+hyposmia (n=41) or nonRBD-hyposmia (n=41) groups based on the RBD Screening Questionnaire (RBDSQ) [3] (cut-off 7) and an olfactory test (B-SIT [4]/ Sniffin’Stick [5]). Both groups were age- and gender-matched. No significant differences were observed for years of education between the groups. The Montreal Cognitive Assessment (MoCA) [6] and the Informant Questionnaire on Cognitive Decline In Elderly (IQCode) [7] were applied to assess global cognition and changes in everyday cognitive functions.

Results: The group with pRBD and hyposmia showed lower scores in the MoCA compared to the matched group without RBD and hyposmia. In a larger sample (n=202) the pRBD group additionally showed significant higher scores in the IQCode compared to the age- and gender-matched control subjects. According to the MoCA, subitems assessing executive functions and visuospatial functions were significantly lower in pRBD+hyposmia.

Conclusion: In line with the literature on prodromal PD [2], our results show that global cognition, executive functions and visuospatial functions are impaired in pRBD+hyposmia. Broader neuropsychological assessments, polysomnography and increased sample size are foreseen in the coming weeks to validate the results in the full sample of the Luxembourgish RBD study. Furthermore, longitudinal analysis will evaluate conversion rates to synucleinopathies.

References: [1] Heinzel S, Berg D, Gasser T, Chen H, Yao C, Postuma RB (2019) Update of the MDS research criteria for prodromal Parkinson’s disease. Movement Disorders 34, 1464–1470.
[2] Fengler S, Liepelt-Scarfone I, Brockmann K, Schäffer E, Berg D, Kalbe E (2017) Cognitive changes in prodromal Parkinson’s disease: A review, John Wiley and Sons Inc.
[3] Nomura T, Inoue Y, Kagimura T, Uemura Y, Nakashima K (2011) Utility of the REM sleep behavior disorder screening questionnaire (RBDSQ) in Parkinson’s disease patients. Sleep Medicine 12, 711–713.
[4] Doty RL, Marcus A, William Lee W (1996) Development of the 12-item cross-cultural smell identification test(cc-sit). Laryngoscope 106, 353–356.
[5] Hummel T, Sekinger B, Wolf SR, Pauli E, Kobal G (1997) “Sniffin” sticks’: olfactory performance assessed by the combined testing of odor identification, odor discrimination and olfactory threshold. Chemical senses 22, 39–52.
[6] Nasreddine ZS, Phillips NA, Bédirian V, Charbonneau S, Whitehead V, Collin I, Cummings JL, Chertkow H (2005) The Montreal Cognitive Assessment, MoCA: A brief screening tool for mild cognitive impairment. Journal of the American Geriatrics Society 53, 695–699.
[7] Jorm AF (1994) A short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): development and cross-validation. Psychological medicine 24, 145–153.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/preliminary-results-on-the-cognitive-profile-in-prodromal-parkinsons-disease-a-prospective-study/