0813 Circadian Rest-activity Rhythm In Isolated Rem Sleep Behavior Disorder

Isolated REM sleep behavior disorder (iRBD) is a parasomnia characterized by abnormal behaviours occurring during REM sleep. Several studies showed that iRBD is a prodromal stage of synucleinopathies. Therefore identifying iRBD in the general population is of utmost importance. Aim of this study was to explore whether the assessment of circadian rest-activity rhythm features, measured by actigraphy, can distinguish iRBD patients from patients suffering from disorders characterized by other pathological motor activity during sleep and healthy controls. Methods Nineteen subjects with video-polysomnographic (v-PSG) diagnosis of iRBD, 39 subjects with other disorders with motor activity during sleep (19 restless leg syndrome -RLS- and 20 untreated sleep apnea syndrome patients -SAS) and 16 healthy controls underwent 2-week actigraphy, v-PSG, and completed RBD screening questionnaires. Nonparametric analyses were applied to assess rest-activity rhythm features; daytime napping was also evaluated. The diagnostic value of nonparametric measures has been assessed through ROC curve. Results iRBD patient showed lower sleep efficiency, increased WASO and increased frequency of prolonged activity bouts compared to RLS and controls, while no difference emerged with SAS patients. Moreover, iRBD patients presented increased occurrence of estimated nap in comparison to RLS, SAS and controls. The nonparametric measure I<O distinguished iRBD patients from RLS, SAS and controls with an area under the curve greater than that of RBD screening questionnaires. Conclusion The nonparametric index I<O is able to distinguish iRBD patients from patients with other pathological motor activity during sleep and controls, confirming its potential use as an objective measure suitable to screen large at-risk populations. Support This study was supported by a grant from the Austrian Science Fund (FWF) to Birgit Högl, I 2120-B27.