Continued Validation of the RBD Symptom Severity Scale (RBDSSS) in Participants of the North American Prodromal Synucleinopathy (NAPS) Consortium
Andrea Busicescu1, Parichita Choudhury2, Joyce Lee-Iannotti3, Pooja Rangan3, Maria Livia Fantini4, David Shprecher2, Miranda Lim5, John Elliott6, Alon Avidan7, Daniel Huddleston8, Donald Bliwise8, Michael Howell9, Carlos Schenck10, Susan Criswell11, Chengjie Xiong11, Jennifer McLeland12, Emmanuel During13, Emmanuel Mignot14, Amelie Pelletier15, Jean-Francois Gagnon16, Leah Forsberg17, Julie Fields17, Erik St. Louis17, Aleksandar Videnovic18, Yo-El Ju11, Bradley Boeve17, Ronald Postuma15
1University of Arizona College of Medicine - Phoenix, 2Banner Sun Health Research Institute, 3Banner University Medical Center, 4Le Centre Hospitalier Universitaire, 5Oregon Health & Science University, 6Ohio Health, 7David Geffen School of Medicine at UCLA, 8Emory University, 9University of Minnesota, 10Minnesota Regional Sleep Disorders Center, 11Washington University, 12Washington University School of Medicine, 13Stanford, 14Stanford University, 15Montreal General Hospital, 16Centre D'etude Du Sommeil, 17Mayo Clinic, 18MGH Neurological Clinical Research Institute
Objective:
The objective of this study is to assess the validity of the REM Sleep Behavior Disorder (RBD) symptom severity scale (RBDSSS) and its correlation to the clinical global impression of severity (CGI-S) in a cohort of participants from the North American Prodromal Synucleinopathy (NAPS) study.
Background:
REM sleep behavior disorder (RBD) is a parasomnia characterized by dream enactment and is a prodromal marker of α-synucleinopathies. There is currently no standardized tool for assessing symptom severity in clinical or research practice. To fill this gap, the International RBD Study Group developed the RBDSSS, an 8-item questionnaire which assesses frequency and severity of dream content, vocalizations, movements, and injuries associated with RBD.
Design/Methods:
Participants and their bedpartners enrolled in the NAPS cohort filled out the RBDSSS questionnaire. Total scores for participant (maximum score=54) and bedpartner (maximum score=38) questionnaires are derived by multiplying frequency and severity scores for each question. A clinical global severity index and RBD symptom frequency was assessed by clinical interview with patients +/- bedpartners. Descriptive analysis and correlations between scores and sub-items were assessed, and item response analysis was conducted.
Results:
Among 261 study participants, the median (interquartile range) score for the RBDSSS-participant was 10 (4-18), and that of the RBDSSS-bedpartner was 8 (4-15). The median CGI-S was 3 (3-4), indicating moderate severity. RBDSSS-bedpartner scores were significantly lower in women (6 vs. 9, p=0.02) while there were no sex differences in RBDSSS-participant scores (8 vs. 10.5, p=0.615). We found strong correlations between RBDSSS-participant vs. RBDSSS-bedpartner (Spearman rs=0.561), RBDSSS-participant vs. CGI-S (rs=0.556), and RBDSSS-bedpartner vs. CGI-S (rs=0.491, all p<0.0001). Item response analysis showed a high discriminatory value for RBDSSS-participant (range 1.40-2.12) and RBDSSS-bedpartner (1.29-3.47).
Conclusions:
The RBDSSS has adequate psychometric properties to quantify RBD severity, with good concordance between participant and bedpartner questionnaires and between scale scores and global severity.