Impaired Dynamic Cerebral Autoregulation Across the REM Sleep Behavior Disorder Spectrum: Evidence From Isolated REM Sleep Without Atonia to Parkinson's Disease With RBD.
Zhang Y, Piao Y, et al. • CNS neuroscience & therapeutics • 2026
Dynamic cerebral autoregulation, measured as transfer function phase difference, was impaired in patients with isolated RSWA, isolated RBD, and PD with RBD compared with healthy controls, and reduced phase difference was associated with lower REM sleep amount and greater phasic RSWA, suggesting dCA dysfunction may be an early pathophysiological feature in RBD-related neurodegeneration.
Key Findings
Methods
The study compared four groups: patients with iRSWA, iRBD, PD+RBD, and healthy controls.
A total of 25 patients with iRSWA, 30 with iRBD, 28 with PD+RBD, and 30 healthy controls were included.
Controls were age- and sex-matched.
The design was a case-control study using video-polysomnography and magnetic resonance imaging.
Dynamic cerebral autoregulation was assessed with transcranial Doppler and finger plethysmography, analyzing phase difference by transfer function analysis; autonomic function was assessed with SCOPA-AUT.
Results
REM sleep percentage was significantly lower in the iRBD and PD+RBD groups than in controls.
The abstract reports this reduction for the iRBD and PD+RBD groups specifically.
The iRSWA group is not described as differing from controls in REM sleep percentage.
Results
Phasic RSWA, but not tonic RSWA, differed significantly among the three patient groups.
The abstract reports "p < 0.001" for the difference in phasic RSWA across iRSWA, iRBD, and PD+RBD.
Tonic RSWA did not differ significantly among the three patient groups.
Results
Phase difference, a measure of dynamic cerebral autoregulation, was significantly lower in all three patient groups than in controls.
The abstract reports "p < 0.001" for the comparison of each patient group with healthy controls.
The reduction was present even in the iRSWA group, which is considered a potential early stage of the RBD spectrum.
Phase difference was derived from transfer function analysis of transcranial Doppler and finger plethysmography recordings.
Results
Phase difference was significantly associated with REM sleep amount and with phasic RSWA.
Both associations were reported with "p < 0.001".
Reduced phase difference was linked to lower REM sleep amount and greater phasic RSWA.
Conclusions
The authors conclude that dCA is impaired across iRSWA, iRBD, and PD+RBD and may represent an early pathophysiological feature of RBD-related neurodegeneration.
They suggest the findings reflect disrupted coupling among REM sleep regulation, autonomic function, and cerebrovascular control.
iRSWA has been proposed as a potential early stage within the RBD spectrum, and its physiological significance remained incompletely understood.
What This Means
This study looked at how well the brain keeps its blood flow steady in people along a spectrum of REM sleep problems. REM sleep behavior disorder (RBD) involves acting out dreams because muscles do not go limp during REM sleep. It is often an early sign of diseases such as Parkinson's. The researchers compared 25 people with isolated REM sleep without atonia (muscle activity during REM sleep without dream enactment), 30 with isolated RBD, 28 with Parkinson's disease plus RBD, and 30 healthy controls of similar age and sex.
All three patient groups showed weaker dynamic cerebral autoregulation, the brain's ability to adjust blood flow to changes in blood pressure, than healthy controls. This included people with only the earliest, mildest form (isolated REM sleep without atonia). Patients with isolated RBD and Parkinson's plus RBD also had less REM sleep. Bursts of muscle activity during REM sleep (phasic) differed among patient groups, while sustained muscle activity (tonic) did not. Poorer blood flow regulation went along with less REM sleep and more phasic muscle activity.
This research suggests that problems with brain blood-flow control may appear early in the course of RBD-related neurodegeneration, possibly linking REM sleep regulation, the autonomic nervous system, and brain blood vessels. Because this was a case-control study, it shows associations rather than cause and effect, and it does not by itself show whether these measures could be used to predict who develops disease.
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Zhang Y, Piao Y, Sun Q, Li H, Wang Y, Lu J, et al.. (2026). Impaired Dynamic Cerebral Autoregulation Across the REM Sleep Behavior Disorder Spectrum: Evidence From Isolated REM Sleep Without Atonia to Parkinson's Disease With RBD.. CNS neuroscience & therapeutics. https://doi.org/10.1002/cns.71190