To investigate differences in Heart Rate Variability (HRV) during NREM and REM sleep between Parkinson’s Disease (PD) and healthy controls (HC).

We analyzed demographics, sleep architecture, and polysomnography-derived ECG data from 36 individuals with PD and 20 HC subjects. We performed frequency-domain analysis on 2-minute epochs from abutting REM and NREM segments to determine low-frequency (LF) power, high-frequency (HF) power, and LF/HF ratio. We also conducted comprehensive cognitive assessments of the PD individuals. Demographics, sleep characteristics, and HRV outcomes were compared using t-tests, Wilcoxon rank sum tests, and Chi-squared tests as appropriate. Relationships between cognitive domains and HRV outcomes were assessed using Spearman correlations.

Demographic and sleep architecture features were similar between groups except that there were more males in the PD group. Therefore, HRV outcomes were adjusted for sex. Compared to HCs, PD subjects demonstrated lower LF/HF ratio (NREM p=0.046, REM p=0.011), lower LF power (NREM p=0.037, REM p=0.007), and higher HF power (NREM=0.037, REM p=0.007). These differences were greater in REM than in NREM. In the PD group, HF power was positively correlated (p=0.029), whereas LF power (p=0.031) and LF/HF ratio (p=0.031) were negatively correlated with executive function and processing speed domains.

Our findings suggest significant nocturnal autonomic imbalance in PD with reduced sympathetic influence. Because dysautonomia can occur in early stages of PD, HRV may serve as a valuable tool for early, non-invasive detection and monitoring. Correlation with clinical outcomes such as cognitive function can help us better understand the prognostic value of HRV in PD.