Objective: Examine the prevalence of Subjective Cognitive Decline (SCD) in a national population-based survey among participants at risk for RBD

Background: SCD is defined as a self-perceived decline in cognitive abilities, despite maintaining normal scores on standardized cognitive tests[1]. SCD elevates the risk of progressing to Mild Cognitive Impairment(MCI) and/or dementia[2,3] and can already manifest in both the preclinical and prodromal stages of Parkinson’s disease (PD)[4]. Therefore, SCD holds promise as a useful screening marker on a large scale[5]. RBD increases the likelihood of developing alpha-synucleinopathies such as PD and is therefore considered a potent prodromal marker[6].

Method: We performed an online survey inviting all residents of Luxembourg aged between 55 and 75 years. Participants filled out information about age, sex, location,the self-reported Short Informant Questionnaire on Cognitive Decline in the Elderly(SR-IQCODE) and the RBD Screening Questionnaire(RBDSQ).We fitted multivariate logistic regression models testing for interaction terms.

Results: 15 914 participants(54% male)were included with a mean age of 63.6 years(SD 5.3). Mean IQCODE was 3.05(SD 0.42) points. By using a cutoff ≥ 3.31[7], 3,022 participants(19.0%) reported SCD, of which 17.8% were male and 20.4% were female. By language, 17.9%,19.2%,17.6% and 34.2% of people who chose German, French, English or Portuguese reported SCD. The mean RBDSQ score was 4.6(SD 2.8) in people with SCD and 3.1(2.4) without SCD. The final multivariate logistic regression analysis model showed associations of IQCODE with age(OR [95% LCI, UCI])(1.05 [1.02, 1.08]),RBDSQ score(1.66 [1.39, 1.97]),male sex(0.83 [0.76, 0.9]),Portuguese language(1.92 [1.52, 2.42])and with regions in the south of Luxembourg(6.85 [1.13, 41.35]). We also observed significant interactions between age and RBDSQ score(0.99[0.99, 0.99]); the effect of having a high RBDSQ score on cognition diminished when age increased, and interactions between age and canton([0.97[0.95, 0.99]); the older the participants were, the less they had SCD when living in the south of Luxembourg.

Conclusion: SCD was more prevalent in the elderly Luxembourgish population, particularly in the Portuguese speakers and in the south of Luxembourg.This region was previously coined by steel industry potentially affecting socioeconomic factors known to be linked to cognitive decline and higher prevalence of hypertension[8].

References: [1].Jessen F, Amariglio RE, van Boxtel M, et al. A conceptual framework for research on subjective cognitive decline in preclinical Alzheimer’s disease. Alzheimers Dement 2014; 10(6): 844–852.
[2].Jonker C, Geerlings MI, Schmand B. Are memory complaints predictive for dementia? A review of clinical and population-based studies. Int J Geriatr Psychiatry 2000; 15(11): 983–991.
[3].Samieri C, Proust-Lima C, Glymour M, et al. Subjective cognitive concerns, episodic memory, and the APOE ε4 allele. Alzheimers Dement 2014; 10(6): 752–759.e1.
[4].Fengler S, Liepelt-Scarfone I, Brockmann K, et al. Cognitive changes in prodromal Parkinson’s disease: a review. Mov Disord 2017; 32(12): 1655–1666.
[5].Flores-Torres MH, Bjornevik K, Hung AY, Healy BC, Schwarzschild MA, Blacker D, Ascherio A. Subjective Cognitive Decline in Women with Features Suggestive of Prodromal Parkinson’s Disease. Mov Disord. 2023 Aug;38(8):1473-1482. doi: 10.1002/mds.29503. Epub 2023 Jun 14. PMID: 37315105; PMCID: PMC10524634
[6].Postuma RB, Gagnon JF, Montplaisir JY. REM Sleep Behavior Disorder and Prodromal Neurodegeneration – Where Are We Headed? Tremor Other Hyperkinet Mov (N Y). 2013;3:tre-03-134-2929-1. doi: 10.7916/D8N879HS. Epub 2013 Mar 26. PMID: 23532774; PMCID: PMC3607914
[7].Jorm AF. A short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): development and cross-validation. Psychological Medicine. 1994;24:145–53. doi:10.1017/s003329170002691x
[8].Ruiz-Castell M, Kandala NB, Kuemmerle A, Schritz A, Barré J, Delagardelle C, Krippler S, Schmit JC, Stranges S. Hypertension burden in Luxembourg: Individual risk factors and geographic variations, 2013 to 2015 European Health Examination Survey. Medicine (Baltimore). 2016 Sep;95(36):e4758. doi: 10.1097/MD.0000000000004758. PMID: 27603374; PMCID: PMC5023897.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/subjective-cognitive-decline-in-a-national-population-based-probable-rbd-survey/