REM sleep behavior disorder as a shared motor phenotype: A multidimensional clinical study.

Area of Science:

• Neurology
• Sleep Medicine
• Neurodegenerative Diseases

Background:

• REM sleep behavior disorder (RBD) is a heterogeneous condition with various causes.
• These include isolated RBD (often a prodromal synucleinopathy), antidepressant-induced RBD, and RBD linked to tauopathies like Alzheimer's disease.

Purpose of the Study:

• To compare clinical, cognitive, neuroimaging, and polysomnographic features of isolated RBD (iRBD), antidepressant-associated RBD (iatroRBD), and tauopathy-associated RBD (tauRBD).
• To identify distinguishing markers across these RBD subtypes within a single cohort.

Main Methods:

• Retrospective analysis of polysomnographically confirmed RBD patients, excluding established synucleinopathies.
• Classification into iRBD (n=26), iatroRBD (n=16), or tauRBD (n=6) based on established criteria.
• Comparison of demographics, non-motor symptoms, MMSE, neuroimaging, and polysomnography using non-parametric statistics.

Main Results:

• Cognitive performance significantly differed, with tauRBD patients exhibiting lower MMSE scores.
• Sex distribution varied, showing male predominance in iRBD but a more balanced distribution in iatroRBD and tauRBD.
• Polysomnography revealed differences in REM sleep architecture: reduced REM percentage in tauRBD and prolonged REM latency in iatroRBD.

Conclusions:

• RBD can manifest as a shared motor phenotype across different etiological contexts.
• Cognitive status, sex distribution, and specific REM sleep features are key discriminators.
• Non-motor symptoms and routine PSG metrics showed limited value in differentiating RBD subtypes in this retrospective study.