Lower heart rate variability (HRV) during sleep may serve as an early indicator of neurodegeneration in patients with idiopathic REM sleep behavior disorder, according to findings presented at the 11th Congress of the European Academy of Neurology.

In a matched case-control study, investigators from the University Hospital Inselspital in Bern, Switzerland, analyzed sleep-related autonomic function in patients with idiopathic REM sleep behavior disorder (iRBD), a condition recognized as a prodromal stage of Parkinson disease and other alpha-synucleinopathies.

Using data from the Bern Sleep-Wake Registry (N ≈11,000), the researchers identified 17 patients with iRBD and matched them in a 1:6 ratio with 102 control subjects without known brain damage. Matching criteria included age, sex, and apnea-hypopnea index. All participants underwent overnight clinical polysomnography to assess nocturnal HRV.

Twenty HRV parameters—comprising time-domain, frequency-domain, and nonlinear measures—were extracted from the recordings. Patients with iRBD exhibited significantly lower HRV compared with controls, particularly in the absolute power of low-frequency (LF) and high-frequency (HF) components, suggesting impaired autonomic modulation during sleep.

During a total follow-up of 132 person-years, 3 of the 17 patients with iRBD were subsequently diagnosed with Parkinson disease. Exploratory analyses showed that these patients had higher mean nocturnal heart rates, lower HRV, and increased sympathetic dominance compared with iRBD patients who did not convert.

These findings support the hypothesis that autonomic dysfunction may precede the clinical onset of neurodegenerative disease. HRV during sleep, as assessed by noninvasive polysomnography, may represent a potential biomarker for identifying patients with iRBD at higher risk of developing Parkinson disease.

Although limited by a small sample size, the study benefits from the use of age- and apnea-index–matched controls and standardized data from a large sleep registry. The investigators emphasized the need for larger prospective trials to validate the utility of sleep HRV as a predictive biomarker of disease progression in iRBD.

The authors declared having no competing interests.

Source: Filchenko I, Serrano Lopes L, van der Meer J, Bassetti C, Schäfer C. Nocturnal heart rate variability in iRBD. European Journal of Neurology. 2025;30(Suppl 1):EPR-253. Presented at: 11th Congress of the European Academy of Neurology; June 2025; Helsinki, Finland.