Objective: We aim to investigate for the first time whether it is possible to detect a predisposition for upcoming Freezing of Gait (FoG) events from Autonomic Nervous System (ANS) activity measured at rest (while standing).

Background: FoG is a debilitating symptom of advanced Parkinson’s disease (PD) characterized by a sudden, episodic stepping arrest despite the intention to continue walking. The etiology of FoG is still unknown, but accumulating evidence unraveled physiological signatures of the ANS around FoG episodes.

Method: We recorded heart-rate for one-minute while standing in 24 persons with PD with FoG (PD+FoG), while OFF levodopa medications, and in 21 elderly controls (EC). Then, PD+FoG participants performed walking trials containing FoG-triggering events (e.g., turns). During these trials, n=13 did experience FoG (PD+FoG+), while n=8 did not experience it (PD+FoG-). Most PD participants (n=16: 9 PD+FoG+ and 7 PD+FoG-) repeated the experiment 2-3 weeks later, while ON levodopa medications, and none experienced FoG. We then analyzed heart-rate variability (HRV), i.e., the fluctuations in time intervals between adjacent heart-beats. HRV is mainly generated by heart-brain interactions and it is considered a marker of sympathetic/parasympathetic balance. Higher HRV (or greater variability between heartbeats) indicates balanced sympathetic/parasympathetic activity and reflects greater adaptability to the environment.

Results: During OFF, HRV was significantly lower in PD+FoG+ participants, reflecting imbalanced sympathetic/parasympathetic activity and disrupted self-regulatory capacity. PD+FoG- and EC participants showed comparable (higher) HRV. During ON, HRV did not differ among groups. HRV parameters at rest did not differ from HRV parameters collected during walking. Finally, HRV values did not correlate with age, PD duration, levodopa consumption, nor motor-symptoms severity scores.

Conclusion: Overall, these results support our hypothesis of a relation between HRV at rest and FoG presence/absence during gait trials, ultimately extending accumulating evidence documenting increased interactions between the central and autonomic nervous systems in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/heart-rate-variability-as-a-new-marker-for-freezing-predisposition-in-parkinsons-disease/