Factors Influencing the Presentation of REM Sleep Behavior Disorder: The Relative Importance of Sex, Associated Neurological Disorder, and Context of Referral to Polysomnography

Study Objectives: To identify the interrelation and relative influence of sex, associated neurological disorder, and polysomnography (PSG) context on the manifestations of rapid eye movement (REM) sleep behavior disorder (RBD). Methods: Fifty-seven patients with RBD were assessed with video PSG regarding sleep structure, muscular activity, and motor events (ME) during REM sleep. Patients were categorized according to sex, associated neurological disorder (clinically isolated RBD [iRBD] versus RBD associated with an overt alpha-synucleinopathy [sRBD]) and motive for PSG (direct referral due to RBD symptoms [First, n = 14]; referred after screening procedures [Screening, n = 13]; referred during clinical follow-up for other disorders [Follow-up, n = 22]; referred for symptoms other than RBD [Incidental, n = 8]). Results: Phasic muscular activity index and the relative number of myoclonic and trunk ME were significantly higher in males and segmental ME in female patients. sRBD was associated with Screening and iRBD with First categories. There was a higher severity of ME in patients with iRBD. Global motor severity of ME was significantly higher in the First category. In multivariate analysis, both motive for PSG and associated neurological disorder had a significant and independent influence in the global severity of ME. Conclusions: Associated neurological disorder and motive for PSG can significantly influence RBD presentation. Male sex is related with higher muscular phasic activity and a different pattern of ME, which could contribute to prevalence variations across studies. Having iRBD and being directly referred for a first consultation because of complaints compatible with RBD are interrelated and contribute independently to a higher severity of ME.