The vagus nerve regulates autonomic function and heart rate variability (HRV). Auricular tVNS may improve autonomic balance by enhancing parasympathetic activity. In this controlled study, a single one-hour session of tVNS increased vagal activity by 48%, measured through the High Frequency (HF) component of HRV. The LF/HF ratio also emerged as a key marker predicting responsiveness to stimulation.

The vagus nerve is a central pathway of the parasympathetic nervous system, responsible for maintaining balance across multiple physiological systems and promoting recovery following stress. Its function can be directly assessed through heart rate variability (HRV), which measures the subtle fluctuations in the intervals between heartbeats. These small variations reflect the body’s ability to adapt to internal and external demands.

High HRV indicates greater autonomic flexibility, resilience, and capacity for relaxation, while low HRV reflects reduced adaptability and sustained sympathetic dominance, often linked to stress and negative health outcomes. For this reason, HRV serves as a robust and widely accepted biomarker of vagal activity and stress regulation.

⦁ Design: Randomised, placebo controlled longitudinal study.

⦁ Participants: N=32, ages 18–31

⦁ Intervention:
- Active group: 1 single stimulation session using a Roga tVNS device, applied for 1-hour
- Placebo group: Identical sham device that mimicked setup but delivered no effective stimulation.
‍
⦁ Lab Equipment: Participants were equipped with a five-lead Shimmer ECG, which was collected at 512 Hz with Shimmer ConsensysPro software (v.1.6.0, Shimmer Sensing, Dublin, IR).
- The ECG record from Lead II was imported into ARTiiFACT software (v2.13) to extract the interbeat intervals (IBIs) and compute the values.

⦁ Measurements: mean heart rate (HR), Low Frequency spectral power [0.04–0.15 Hz] (LF), High Frequency spectral power [.15 to .4 Hz] (HF), LF/HF Ratio, and Percentage of successive Normal-to-Normal intervals >50ms apart (pNN50).

Active tVNS stimulation produced a marked increase in parasympathetic activity compared to placebo. Most notably, HF power, a direct index of vagal tone, increased by 48% under active stimulation, demonstrating significant effectiveness. While both active and sham conditions showed some change over time, the active group exhibited clearer and more sustained autonomic modulation.

The high frequency (HF) component of HRV (Fig. A) is the clearest marker of vagal activity and parasympathetic tone. Under active stimulation, HF power increased by +37% at 20 minutes and by +48% at 1 hour, demonstrating a strong and sustained enhancement of vagal activity, while the sham condition showed no recovery.

The LF/HF ratio (Fig. C) reflects the balance between sympathetic and parasympathetic influences. In the active group, this ratio declined by –27%, indicating a progressive shift toward parasympathetic dominance. In contrast, the sham group showed increases over the same period, consistent with sympathetic predominance.

The low frequency (LF) component (Fig. B) showed minor fluctuations, suggesting a limited role in distinguishing sympathetic from parasympathetic activity.

RMSSD is a key index of HRV, reflecting short term beat-to-beat variability in heart rhythms. Because RMSSD is strongly linked to vagal modulation, higher values indicate stronger parasympathetic activity and better autonomic flexibility. Under the active tVNS session, RMSSD increased by +17% (Fig. D), while the sham condition showed only minimal change. This finding suggests enhanced parasympathetic regulation.

pNN50 provides another sensitive measure of parasympathetic tone, capturing the proportion of large fluctuations in heartbeats. Active stimulation produced a +14% increase in pNN50 at 1 hour (Fig. E), compared with a smaller change in the sham condition. These results confirm that the stimulation led to consistent improvements in parasympathetic activity.

Vagus nerve stimulation significantly enhanced parasympathetic activity. HF power increased by 48% in a single 1 hour Roga session, indicating a clear shift toward vagal dominance. HRV indices such as RMSSD and pNN50 also rose, reflecting greater beat-to-beat variability and autonomic flexibility. Together, these results demonstrate that Roga strengthened vagal regulation and improved stress-related autonomic balance.

Future studies should confirm these effects using longer protocols, larger cohorts, and expanded biometrics to better establish their therapeutic potential.

Keywords

Vagus Nerve, Heart Rate Variability (HRV), Parasympathetic Activity, Autonomic Nervous System, RMSSD, pNN50, High Frequency HRV, Low Frequency HRV