Objective: To examine the frequency of RBD in PSP and its associations with other non-motor symptoms.

Background: RBD once considered rare in PSP, is now increasingly recognised with reported prevalences of 20–30%.¹^–³ It remains unclear whether RBD in PSP represents a true non-motor symptom of PSP or reflects co-existing α-synuclein pathology.⁴

Method: Patients diagnosed with PSP according to the MDS-PSP criteria⁵, were consecutively recruited from the Movement Disorders Clinic of our centre from September 2024 to September 2025. Age- and gender-matched controls were also recruited after screening with Tanner’s questionnaire for parkinsonism. All PSP cases underwent assessment using the PSP Rating Scale(PSPRS), RBD Screening Questionnaire (RBDSQ), Non-Motor Symptoms Scale (NMSS),MoCA, Frontal Assessment Battery(FAB), Beck Depression Inventory(BDI), Parkinson’s Disease Sleep Scale(PDSS), Parkinson’s Disease Questionnaire-39(PDQ-39), and a hyposmia rating scale. Controls completed the RBDSQ. Data were analysed using descriptive statistics, t-tests, chi-square tests, and multiple linear regression to identify predictors of RBD.

Results: A total of 150 PSP cases (101 males, 49 females) and 150 controls (95 males, 55 females) were recruited. The mean age at first clinic visit was 69.1±7.5 years, and mean disease duration was 3.61±2.1 years. Clinically probable RBD was present in 28 PSP cases (18.6%) and in none of the controls. RBD occurred in 11 individuals (39.3%) with PSP-RS and 14 individuals (50%) with PSP-P. RBD was associated with higher NMSS scores (29.71±21.35 vs 15.14± 2.72; p = 0.002) and worse PDQ-39 scores (38.54±16.30 vs 32.62±13.00; p = 0.041). PSPRS scores did not differ significantly between those with and without RBD (31.57±15.24 vs 29.11±14.97; p = 0.43)(Table1). The attention/memory and gastrointestinal domains of the NMSS were significantly higher in the RBD group and showed significant positive associations with RBD (β = 0.205, p = 0.011; β = 0.250, p = 0.003, respectively).

Conclusion: RBD occurred in 18.7% of PSP cases in our study and was observed in both PSP-RS and PSP-P subtypes, consistent with previous reports.⁶,⁷ Reported RBD frequencies in PSP are substantially higher than the prevalence of idiopathic RBD in the general population (0.6–1%).⁸ These findings support the concept that RBD in PSP may represent genuine PSP‑related phenomenon rather than a coincidental comorbidity.

Table 1: PSP patients with and without RBD

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rem-sleep-behaviour-disorder-rbd-and-its-relation-to-non-motor-symptoms-in-progressive-supranuclear-palsypsp/