Assessment of ventricular repolarization variability in wake states in REM sleep behaviour disorder and Parkinson's diseases

Idiopathic REM Sleep Behaviour Disorder (iRBD) patients exhibit autonomic dysfunction, increasing cardiovascular mortality risk. Despite this, the link to cardiovascular mortality is underexplored. This pilot study investigates the QT-variability (QTV) in iRBD and RBD with Parkinson’s disease (PD-RBD) during wake before (WBS) and after (WAS) sleep. This study included 18 control (CG), 20 iRBD, and 20 PD-RBD participants. QTV and RR variability (RRV) were derived from a 5-minute ECG epoch of polysomnography data during the two wake states. Analyses included time and frequency domain indexes, followed by non-parametric statistical analysis to assess intra- and inter-group patterns. Significant differences in frequency domain RRV and QTV unrelated to RRV (QTVuRRV) indexes were found in WAS compared to WBS for both iRBD and PD-RBD. Moreover, iRBD and PD-RBD exhibited a significant reduction in low- and high-frequency RRV indexes and QTVuRRV compared with the CG. In conclusion, RRV and QTVuRRV findings suggest altered autonomic regulation in iRBD and PD-RBD. However, the lack of differences in QTV indexes might suggests no significant risk of cardiovascular mortality.