Early parasympathetic dysfunction in Parkinson's disease: insights from information-theoretic analysis

Area of Science:

• Neurology
• Cardiology
• Autonomic Neuroscience

Background:

• Parasympathetic nervous system (PNS) dysfunction is a known feature of Parkinson's disease (PD), but early impairment remains poorly understood.
• Previous heart rate variability (HRV) studies in PD have yielded inconsistent results regarding autonomic function.
• Constipation, a non-motor symptom, is often indicative of underlying autonomic dysfunction in PD.

Purpose of the Study:

• To evaluate cardiovascular PNS function in early-stage PD using conventional and advanced analytical methods.
• To investigate the baroreflex-mediated mechanisms of respiratory heart rate variability (RespHRV) in PD.
• To explore the relationship between constipation and autonomic dysfunction in PD patients.

Main Methods:

• Assessed 16 early-stage PD patients and 16 controls using HRV analysis during supine rest, head-up tilt, and recovery.
• Employed multiscale Partial Information Decomposition (PID) to differentiate baroreflex-mediated RespHRV.
• Measured cardiac baroreflex sensitivity (BRS) using causal estimation and PID-derived parameters.

Main Results:

• Early-stage PD patients exhibited parasympathetic impairment, particularly during orthostatic stress (head-up tilt).
• Reduced high-frequency (HF) power during tilt and significantly lower causal BRS were observed in PD patients.
• PID analysis revealed impaired baroreflex-mediated RespHRV during tilt in PD, more pronounced in those with constipation.

Conclusions:

• Findings support the α-Synuclein Origin and Connectome model, suggesting peripheral autonomic nervous system involvement in early PD.
• Early-stage PD is characterized by significant cardiac autonomic dysfunction, particularly affecting baroreflex control.
• Constipation may serve as a clinical marker for more severe autonomic impairment in PD.