Objective: Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia frequently affecting patients with synucleinopathies, but its exact prevalence in multiple system atrophy (MSA) is unclear. Whether questionnaires alone are sufficient to diagnose RBD is also unknown.
Methods: We performed a cross-sectional study of patients with probable MSA from six academic centers in the US and Europe. RBD was ascertained clinically and with polysomnography; we also performed a meta-analysis according to PRISMA guidelines for studies published before September 2014 that reported the prevalence of RBD in MSA. A random-effects model was constructed using weighted prevalence proportions. Only articles in English were included. Studies were classified into those that ascertained the presence of RBD in MSA clinically and with polysomnography. Case reports or case series (≤ 5 patients) were not included.
Results: Forty-two patients completed questionnaires and underwent polysomnography. Of those, 32 (76.1%) had clinically suspected RBD and 34 (81%) had polysomnography-confirmed RBD. Two patients reported no symptoms of RBD but had polysomnography-confirmed RBD. The primary search strategy yielded 374 articles of which 12 met the inclusion criteria. The summary prevalence of clinically suspected RBD was 73% (95 % CI, 62-84%) in a combined sample of 324 MSA patients. The summary prevalence of polysomnography-confirmed RBD was 88 % (95% CI, 79-94%) in a combined sample of 217 MSA patients.
Interpretation: Polysomnography-confirmed RBD is present in up to 88% of patients with MSA. RBD was present in some patients that reported no symptoms. More than half of MSA patients report symptoms of RBD before the onset of motor deficits.