Association of heart rate variability with REM sleep without atonia in idiopathic REM sleep behavior disorder

Abstract

Study Objectives: Idiopathic rapid eye movement sleep behavior disorder (iRBD), characterized by rapid eye movement sleep without atonia (RSWA) and dream-enactment behavior, has been suggested to be a predictor of α-synucleinopathies. Autonomic instability, represented by heart rate variability, is a common characteristic of both iRBD and α-synucleinopathies. Previous studies reported that RSWA was associated with autonomic dysfunction and was a possible predictor of phenoconversion. Therefore, we sought to compare heart rate variability between iRBD and control groups and explore the relationship between heart rate variability and RSWA in patients with iRBD. Methods: Nocturnal polysomnographic data on 47 patients (28 men, 19 women) diagnosed with iRBD based on video-polysomnography and 26 age-matched and sex-matched controls were reviewed. The first 5-minute epoch with a stable electrocardiogram lead II on video-polysomnography was selected from stage N2, wake, and rapid eye movement. For quantification of RSWA, tonic activity was analyzed from the submentalis electromyogram and phasic activity from the submentalis and bilateral anterior tibialis electromyogram channels. Results: Compared to the control group, the iRBD group showed significant reductions in the standard deviation of the R-R intervals, the root mean square of successive R-R interval differences, and high-frequency values. Quantified tonic activity was inversely correlated with normalized low-frequency values and low-frequency/high-frequency ratios and positively correlated with normalized high-frequency values. Conclusions: This study implied decreased cardiac autonomic function in patients with iRBD, which showed parasympathetic predominance. Heart rate variability of the patients with iRBD in this study was associated with quantified tonic RSWA, which was previously reported to be a possible predictor of phenoconversion.

Characterization of Autonomic Dysfunction in REM Sleep Behavior Disorder

“…HF content was observed in N3 and REM stages, which suggests a reduced mostly vagal activity and respiratory influence. These results are generally in agreement with those obtained in [7], in which a lower variance in all sleep stages is shown, in comparison to healthy control, as well as the findings achieved in [6], where the authors highlighted the autonomic impairment with lower values in LF RR , HF RR and LF/HF RR for RBDs. The longitudinal characterization of HRV features during different sleep stages showed a general progressive imbalance toward the vagal activity while progressing from N1 to N2 in both populations, and a spiking sympathetic activation in the REM stage.…”

“…In particular, a first-level PSG is needed, requiring the recordings of electroencephalogram (EEG) for sleep scoring, EOG for eye movements assessment, ECG for heart state and heart rate assessment, electromyography (EMG) to demonstrate abnormal muscle activity during REM sleep, usually done by recording the activity of the mylohyoid muscle, and video recordings, to correlate clinical events with the electrophysiological recordings. Analysis of heart rate variability (HRV) parameters in RBD subjects with respect to a healthy control group has already been proposed and it mainly showed reduced variability in the RBD [6,7] group. In [6], a sympathetic impairment was mainly pointed out, with lower values in the power of the low frequency (LF) band and in the sympathovagal balance LF/HF in RBD subjects than controls, but also higher ratios in REM sleep than in stage N2, and lower high-frequency (HF) power values.…”

“…Analysis of heart rate variability (HRV) parameters in RBD subjects with respect to a healthy control group has already been proposed and it mainly showed reduced variability in the RBD [6,7] group. In [6], a sympathetic impairment was mainly pointed out, with lower values in the power of the low frequency (LF) band and in the sympathovagal balance LF/HF in RBD subjects than controls, but also higher ratios in REM sleep than in stage N2, and lower high-frequency (HF) power values. Bugalho et al [7] showed a lower HRV in patients with RBD, with less variations between stages when compared with patients without RBD, especially regarding the HF measures.…”

Predictors of RBD progression and conversion to synucleinopathies

“…Alterations in beat-to-beat variability in a cohort of iRBD patients studied longitudinally for an average 6.7 years, however, did not discriminate between patients who eventually converted from those who did not [ 17 ]. Very recently, presence of low HRV in a cohort of 47 iRBD was associated with severity of the quantified tonic REM Sleep without Atonia (RSWA), an electrophysiological marker of severity of RBD and possible predictor of phenoconversion [ 18 ].…”

“…Faster progression in PD converters [ 13 ••, 14 ••] Quantitative autonomic scales scores Urinary symptoms scores more severe in MSA converters, decline in systolic blood pressure more pronounced in DLB converters [ 13 ••, 15 ] Heart Rate Variability Decreased in iRBD patients. Conflicting results on its predictive value [ 16 , 17 , 18 ] Cognitive dysfunction Alterations in attention, executive function, and verbal memory associated with faster conversion in iRBD. DLB converters show more pronounced cognitive alterations at baseline and faster progression [ 13 ••, 19 , 20 , 21 ] Hyposmia Associated with higher risk of phenoconversion in iRBD to DLB and PD, but not MSA [ 13 ••, 22 , 23 , 24 , 25 ] Visual dysfunction Abnormal colour vision associated with increased risk of phenoconversion.…”