Frequency and characteristic features of REM sleep without atonia.

Objectives: Isolated REM sleep without atonia (iRSWA) is regarded as prodromal phase of REM sleep behavior disorder (RBD) and synucleinopathies. Other factors, however, have also been described to cause RSWA, including sleep apnea, antidepressants use and narcolepsy. We investigated the frequency of RSWA and its different etiologies.

Methods: We investigated RSWA in patients that underwent a clinical video polysomnography. In iRSWA subjects, we examined polysomnography indication and two markers of prodromal Parkinson's disease: excessive daytime sleepiness and depressive symptoms, with a case-control design.

Results: Of the 864 included polysomnographies, 188 were positive for RSWA (21.8%), 17 for RBD (2.0%) and 48 for iRSWA (5.6%). Mean Epworth Sleepiness Scale scores were 9.8 ± 4.8 (iRSWA subjects) and 7.5 ± 4.9 (controls), p = 0.014. Mean Beck Depression Inventory-II scores were 11.3 ± 7.9 (iRSWA subjects) and 9.5 ± 8.4 (controls), p = 0.229. Excessive daytime sleepiness was more often the polysomnography indication in the iRSWA group (p = 0.006).

Conclusions: RSWA is a frequent finding in the context of antidepressant use or synucleinopathies. iRSWA subjects reported increased excessive daytime sleepiness and more often had excessive daytime sleepiness as polysomnography indication.

Significance: Our study provides evidence for high frequency of RSWA, underscoring the need for longitudinal studies in iRSWA patients, with interest for conversion to synucleinopathies.