Background: REM Sleep Behavior Disorder (RBD) is a hallmark of the prodromal phase of α-synucleinopathies. Accurate estimation of the prevalence of probable RBD (pRBD) is crucial for understanding its impact and for planning public health interventions. This study assesses the prevalence of pRBD in the older population of Luxembourg, analyzing demographic, clinical, and geographic factors.

Objectives: To describe the prevalence of pRBD using descriptive statistics and Bayesian prevalence estimation methods. Additionally, to assess the association of pRBD with demographics, clinical characteristics, and geographic distribution.

Methods: In 2021, residents aged 55-75 were invited to an online survey that included the Mayo Sleep Questionnaire (MSQ-1), RBD Screening Questionnaire (RBDSQ), and Short Informant Questionnaire on Cognitive Decline in the Elderly. pRBD was defined by an RBDSQ score ≥7. Descriptive statistics and Bayesian methods were employed to estimate prevalence. Participants with RBDSQ ≥7 were ascertained via telephone interview to confirm pRBD.

Results: From 15,914 participants (54% male, median age 62), the prevalence of pRBD was 12.7%. Bayesian analysis refined this estimate, yielding a mean prevalence of 5.1%, a median of 4.3%, and a mode of 1.7%. The 95% uncertainty interval ranged from 0.2% to 12.1%. The mean sensitivity of the diagnostic test was 98.0%, and the specificity was 92.3%. Significant geographic variability was observed, with higher prevalence rates in the northern canton of Clervaux (mean: 8.8%) and the southern canton of Esch-sur-Alzette (mean: 7.7%).

Conclusions: The study provides robust national estimates of pRBD prevalence, highlighting the impact of methodological approaches on prevalence rates. The findings underscore the need for careful design in online surveys to mitigate bias and enhance diagnostic accuracy.