Auricular Vagal Neuromodulation Therapy (AVNT) significantly increases Vagus Nerve Activity and Heart Rate Variability in Healthy Subjects - Randomised Placebo Controlled Study

Abstract

The vagus nerve plays a critical role in autonomic regulation, influencing stress responses, and multiple mechanisms in various internal organs. This two-stage cross-over study evaluated the impact of Nurosym neuromodulation on heart rate variability (HRV) compared to placebo stimulation. Results demonstrated a significant 61% increase in vagal activity with Nurosym, as indicated by the high frequency (HF) component of HRV, and identified the LF/HF ratio as a predictor of response to neuromodulation. Nurosym neuromodulation effectively enhances parasympathetic function, suggesting potential therapeutic applications for various health conditions. 

Background and aims

The vagus nerve is involved in the regulation of many major systems, the activity of which is a marker of the parasympathetic nervous system and significantly inversely correlates with markers of inflammation. Therefore, increased cardiac vagal activity is proportionally associated with health, well-being, relaxation, and even emotions such as empathy. Conversely, decreased cardiac vagal activity is linked with risk factors such as morbidity, mortality, and stress. Nurosym, as a neuromodulation tool targeting vagal afferents, may have a powerful input to the brain and can influence a large number of autonomic and psychophysiological self-repair mechanisms.

Methods

Two-stages cross-over study compared the effects of Nurosym neuromodulation (tragus) and placebo stimulation (earlobe) on heart rate variability (HRV). Each participant underwent two visits, with the order of stimulation and placebo control randomised. Each visit comprised three phases: a 5-minute baseline period, a 5-minute stimulation period, and a 5-minute recovery period. During the stimulation period, participants received either Nurosym neuromodulation or placebo stimulation, while the effects of stimulation were assessed during the recovery period. Physiological data, including electrocardiogram (ECG) and respiratory data, were continuously recorded throughout the visits. Statistical analyses were performed to compare the effects of Nurosym neuromodulation and placebo stimulation. Various HRV parameters, including time-domain and frequency-domain indices, were analysed to evaluate the effects of stimulation on cardiac autonomic function.

Results

Both the low frequency (LF) and high frequency (HF) components of heart rate variability serve as indicators of vagus nerve activity. The LF component reflects a blend of sympathetic and parasympathetic modulation, while the HF component, detected at 0.15–0.40 Hz, is specifically associated with parasympathetic modulation of heart rate. The study indicated an increase in the activity of the vagus nerve by approximately 61%, as measured by the HF component (*p < 0.0017, Nurosym neuromodulation vs. placebo stimulation), demonstrating significant effectiveness.

(Figure A, B, C, D) The autonomic function response, Nurosym Neuromodulation favourably altered all HRV parameters (A: HF, B: RMSSD, C: pRR50, D: SDRR). Better effects were observed in people with a poorer baseline HRV ratio. Memory effect was observed, meaning HRV remains elevated after neuromodulation was stopped.

Figure (A) shows High Frequency HRV is significantly increased (*p=0.001). Figure (B) shows Low Frequency HRV is significantly decreased (*P=0.001). Figure (C) shows the ratio of LF to HF is significantly decreased (*p=0.002). It suggests a greater shift towards the parasympathetic side during Nurosym neuromodulation, indicating a more pronounced relaxation response.

The Nurosym neuromodulation group was associated with significantly higher measures of cardiac vagal activity compared to the placebo group (time-domain measures and frequency domain ratio). These effects persisted beyond the stimulation period, indicating a carry-over effect. Moreover, baseline LF/HF ratio emerged as a significant predictor of individual response to the vagus nerve neuromodulation, showing that individuals with higher sympathetic activity experienced greater autonomic benefits from the intervention. 

Conclusion

Nurosym vagus nerve neuromodulation activates the parasympathetic nervous system through the vagus nerve, acting as a calming messenger in the body. Nurosym relays information to central vagal projections in the brain stem and higher centres, which, in turn, provide the efferent neural signal to the heart, ensuring the balance between the sympathetic and parasympathetic nervous systems. This connection makes it relevant in the treatment of many diseases, including neurodegenerative diseases, chronic pain, inflammation, and cardiovascular diseases.