Vagus Nerve Activity May Impact Cancer Prognosis

What gives people greater resilience in the face of life-threatening illnesses like cancer? Researchers now believe that vagal nerve activity may contribute to enhanced health and longer life expectancy for individuals with cancer, as well as to enhanced cardiac health and increased resistance against dementia.

What is the Vagus Nerve?

The vagus nerve is an integral part of the parasympathetic nervous system – the branch of the autonomic nervous system responsible for rest, growth, and repair. Recent studies have linked higher levels of vagus nerve activity, as measured by greater heart rate variability (HF-HRV), with longer survival rates in patients with myocardial infarction and acute trauma and in those undergoing palliative care.

The research suggests that vagal nerve activity may also predict survival in patients with metastatic or recurrent breast cancer more reliably than cancer stage alone.  To date, cancer prognoses have largely been determined by tumor stage, age, genetic expression, inflammatory parameters, and organ functioning.

The Relationship of Yoga, the Vagus Nerve, and Cancer Cell Growth

Increasingly, studies are pointing to mindfulness practices like yoga and meditation as stimulating vagus nerve activity. If higher levels of vagus nerve activation influence the progression of advanced-stage cancer, it is possible that such practices may moderate the impact of cancer cell growth and increase life expectancy for those with advanced-stage cancer. Obviously, future studies would be needed to support this proposition.

The activity of the vagus nerve is often referred to as vagal tone. It has been proposed that high vagal tone may slow down tumor growth because it inhibits mechanisms responsible for tumor progression, including oxidative stress, inflammation, and excessive sympathetic nervous system (SNS) activation. In addition, the vagus nerve also innervates major visceral organs where many cancers develop, including the lungs, gut, pancreas, and colon.

Vagal tone is assessed by measuring respiratory sinus arrhythmia. Respiratory sinus arrhythmia refers to the rhythmic increase and decrease in heart rate that occurs synchronously with breathing. During inhalation, heart rate increases (sympathetic nervous system influence), and vagal influence decreases. During exhalation, however, heart rate decreases as vagus influence increases (parasympathetic nervous system activation). Higher respiratory sinus arrhythmia variability levels indicate greater vagal tone, reflecting the body’s ability to respond to increasing metabolic demands and environmental challenges.

Vagal Tone Moderates Tumor Growth in Advance Stage Prostate and Colon Cancer Patients

Vagal tone has been of increasing interest to clinical scientists interested in examining cancer progression because of its relationship to autonomic nervous system function and its innervation of many visceral organs. In one study, researchers in Belgium examined the medical records of 72 individuals with colorectal cancer and 113 individuals with prostate cancer, all of whom had undergone an electrocardiogram (ECG) assessment earlier in their care. ECG provides a measure of respiratory sinus arrhythmia.  They also examined markers of tumor growth i,ncluding Prostate Specific Antigen (PSA) at 6 6-monthollow-up for those with prostate cancer and carcinoembryonic antigen (CEA) for those with colorectal cancer.

For individuals with prostate cancer, the cancer stage, ranging from 1 (a small tumor that has not spread deeply to adjacent tissue) to 4 (metastatic cancer), predicted higher PSA levels at 6-month follow-up but only for individuals with low vagal tone (low HRV). These findings remained the same even after accounting for the effects of age and treatment.

Similarly, the stage of cancer significantly predicted levels of CEA one year later for those with colorectal cancer,  but only in those with low HRV, even after controlling for the effects of age and treatment. Taken together, this means that higher vagal tone was related to lower tumor burden (size of tumor or number of cancer cells in the body) for those with metastatic cancer.

This study is one of the first of its kind to demonstrate the potential moderating factor of vagal tone as measured using HRV in the progression of both prostate and colorectal cancer. The authors suggest that vagal tone should be considered as a potential resiliency factor when determining a cancer prognosis, particularly for those with advanced-stage cancer.

These findings are consistent with other research that finds that people with high vagal nerve activity rebound more quickly from acute stress by showing a more rapid return to baseline levels of inflammatory, endocrine, and cardiovascular function than those with low HRV.

Vagal Tone May Influence Progression of Advanced Stage Breast Cancer

In another study, an international team of researchers set out to examine the relationship between vagal tone and survival rates in 87 women with metastatic and recurrent breast cancer.  During a follow-up period of 7-8 years, participants with high resting HRV had a median survival rate of 34.9% at 37 months, whereas those with low HRV had a mortality rate of 50%. This suggests that women with a high vagal tone may have higher survival rates than those with low vagal activity.

The study’s authors pointed to several possible explanations for this finding. First, they proposed that high HRV may be a marker of the “inflammatory reflex,” in which the vagus nerve informs the brain about tumors and modulates them via feedback to the neuroendocrine and immune systems.

Another possibility is that high vagal activity is linked to self-regulation of emotion and social activity, which may be related to higher breast cancer treatment adherence. Higher vagal activity may also be linked to lower depression and higher levels of social support. Recent investigations find that individuals with higher vagal tone are more resilient to stress, which may be particularly important when undergoing cancer treatment.

Taken together, these studies suggest that high vagal activity may serve as a protective factor that increases survival latency for men and women with prostate, colorectal, and breast cancer. Mindfulness practices like yoga and meditation decrease sympathetic activity, increase parasympathetic dominance, and may stimulate vagal activation. As such, these practices may enhance longevity and quality of life for those diagnosed with cancer. Future studies will be needed to support this proposition.