Perspectives · Physiology

The vagus nerve and heart rate variability

Does the vagus nerve, and the variation in our heartbeat, give us insight into the health not just of our bodies but of our minds?

By Dr Cindy de Villiers · Originally published 2020 · Reviewed and edited July 2026 · General information, not medical advice

In two or three generations, Western societies have gone from boiling water for a bath and hunting animals for subsistence to having hot water, refrigeration, transport, and endless entertainment on tap — not to mention processed food we no longer need to leave home for. Ironically, hunting for food and bathing outside is now a luxury afforded mainly by the rich. We are in clover. And yet we still strive for more. What is this life force that drives us? Is it just longevity, or are we driven by well-being, by a life well lived?

In my observation of patients over many years, those who look back on a life well lived are, paradoxically, more able to accept its ending. Purpose in life — “a self-organising life aim that stimulates goals, promotes healthy behaviours, and gives meaning to life” — is associated with longevity. Psychological well-being, in turn, is associated with better current physical health and function. There appears to be positive reinforcement built into the human organism: a sense of purpose leads to healthy behaviour, and healthy behaviour supports purpose. Neglect that part of human nature and physical health tends to suffer, as if the life force, unattended, slowly leaves.

Despite the reductionism of specialty medicine and Descartes' separation of mind and body, the older Hippocratic view of a body–mind continuum is slowly reappearing in medical research. No clean separation of mind and body has ever been found, nor has a discrete pathway of consciousness. Increasingly, research points to the vagus nerve, and its effect on the heart and the rest of the body, as a kind of “missing link” between the two. Its output, measured as heart rate variability (HRV), connects the physical state of the organism with its responses to physical, emotional, and cognitive challenge.

In layman's terms: all of life is connected, and directly affects the health and well-being of the individual.

The health of the individual influences their choices — diet, movement, substance use — as well as their social engagement and their connection to the environment. These, in turn, feed back to the individual, for better or worse.

The heart is not just a pump

For centuries the heart was considered the source of emotion, courage, and wisdom. In medical school, we were taught instead of a mechanical pump taking its instructions from the brain. Nothing could be further from the truth — and this was already known by the time I trained; but, as they say, it takes the passing of a generation of academics for new research to be accepted.

The heart has its own neural network — the intrinsic cardiac nervous system, sometimes called the “heart-brain” — and it communicates directly with the brain. In fact, the heart sends more signals to the brain than the brain sends to the heart. These reach the brain stem and then the cortex, where we process information and make decisions. The gut, too, has its own neural network, the enteric nervous system, in direct communication with the brain. Your heart and your gut genuinely influence your attention, your motivation, and how you process emotion.

Heart rate variability and the vagus nerve

The autonomic nervous system automatically controls the body's internal workings — you do not have to think about digesting, breathing, or adjusting your heart rate. It is a balance between the parasympathetic (“rest and digest”) and sympathetic (“fight, flight, or freeze”) systems.

Within this system, the vagus nerve stands out as the main controller of the parasympathetic branch. It is the longest cranial nerve, running from the brain stem out to the heart, liver, kidneys, pancreas, oesophagus, intestines, and throat, and it forms part of the heart's neural communication with the brain. It is often described as the “vagal brake” on the sympathetic system: as humans, we can self-regulate and calm the fight-or-flight response, and we do this largely through the vagus nerve. Under constant sympathetic dominance our lives would be short and sharp indeed.

We have our vagus nerves to thank for our humanity.

Measuring vagal activity is therefore a way of reflecting an individual's capacity to self-regulate. In one long-term study, those with the highest self-regulatory abilities were markedly more likely to be alive and free of chronic disease fifteen years later than those with the lowest. As William Osler, one of the founders of Johns Hopkins Hospital, put it: “It is very often much more important what person has the disease than what disease the person has.”

One of the main ways vagal influence is measured is through heart rate variability — the naturally occurring, beat-to-beat changes in heart rate. A healthy HRV reflects good function, capacity, and adaptability. It is not a static number: HRV naturally declines with age, but a higher HRV generally indicates greater health and resilience, and a lower one the opposite.

Day-to-day, HRV can reflect the body's response to challenge. It should drop after an intense training session and then recover, sometimes settling higher than before. It is likely to drop when you are fighting a virus, under emotional stress, or dehydrated. And if you never challenge body or mind with learning, striving, or physical training, HRV may simply drift down with age. I particularly notice how alcohol, or a late meal, lowers mine — which proves a potent motivator. A large study of over 57,000 people has explored the effects of training and alcohol on HRV, supporting its use as a way to identify health and lifestyle effects both for individuals and across populations.

Looking at general health, lower vagal output (low HRV) has been associated in research with increased inflammation, insulin resistance, atherosclerosis, and with mood, digestive, immune, and cognitive health. Higher vagal tone has been associated with neuroprotective effects. None of this makes HRV a diagnosis — it is a signal, best read in context and over time, and for an individual rather than a headline.

Supporting your vagus nerve

You can actively engage the vagus nerve. In the research, higher HRV has been associated with regular exercise, vegetable intake, positive social ties, time spent in nature, and sufficient sleep. Biofeedback and regular breathing exercises — such as slow, rhythmic breathing at around six breaths per minute — have been shown to improve HRV over time, and, interestingly, rhythmically reciting a prayer or mantra has a similar effect. Conversely, negative emotion, smoking, alcohol, air pollution, and nutrient deficiency tend to lower it.

Of particular note is the role of social connection. A lack of social ties has been associated, across ages, with a substantially increased risk of early death over the following years — an effect larger than that of smoking. The vagus nerve appears to promote our very capacity for connecting with others, which is one reason isolation registers so strongly in physical health.

HRV as a metric of purpose

Researchers such as Dr Andrew Kemp and colleagues have published extensively on the relationship between emotion, physical health, and longevity, using HRV as a measure of that integration. Their work suggests vagal function is affected by — and affects — “psychological experience, health behaviours, social ties, as well as the environment,” with the vagus nerve serving as a structural link between physical and mental health. I have drawn on it both in the clinic and in my own life.

With all due respect to the science, I would take the idea a step further. It may be premature to call HRV a measure of “life force.” But given the heart's place in our lives and the vagus nerve's role in our humanity, their coalescence in heart rate variability may be as close as we currently come to a metric of the essence of a life — the will to live, and the desire to thrive.