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Researchers added a vagus nerve stimulator to slow breathing. Heart rate variability went no higher.
That is the short version of a 2023 paper by Szulczewski, D’Agostini and Van Diest in Applied Psychophysiology and Biofeedback. It is a small study, and it tested one set of stimulator settings, so it does not tell us that ear stimulators never do anything. What it does is ask a cleaner question than most of the wellness conversation around the vagus nerve: if you are already breathing slowly, does a device on top add anything you can measure?
What they did
Twenty-two people came in for two sessions. In both, they breathed at six breaths a minute, which is 0.1 Hz, the slow pace that breathing research keeps returning to. In one session they also got transcutaneous auricular vagus nerve stimulation, usually shortened to taVNS: a mild electrical current applied to parts of the outer ear that carry a branch of the vagus nerve. The stimulation was timed to the out-breath, a design meant to work with the breath rather than against it.
In the other session they got a sham: the same kind of device on the earlobe, an area that is not thought to carry that branch. The order was crossed over, so each person served as their own comparison.
The researchers measured the usual markers of vagally mediated heart rate variability: RMSSD (the beat-to-beat change in heart rate), the average interval between beats, and the spectral power of heart rate variability at the breathing frequency.
What they found
Nothing extra. Using both standard and Bayesian statistics, the authors found no effect of real stimulation compared with the sham on any of those measures during slow breathing. Their conclusion is careful: expiratory-gated taVNS, at the parameters they tested, did not produce an acute effect on vagally mediated heart rate variability during slow breathing at 0.1 Hz.
They also note that earlier taVNS studies on heart rate variability were inconsistent to begin with. The reason for trying the combination was a hoped-for synergy. In this sample, the synergy did not show up.
Why this is interesting for a breathing practice
Slow breathing on its own has a much larger evidence base. A 2022 systematic review and meta-analysis by Laborde and colleagues pulled together 223 studies and found that voluntary slow breathing is linked to higher vagally mediated heart rate variability during and after the practice. That review is about slow breathing in general, not alternate nostril breathing in particular, and single-session results vary from study to study. But the overall direction is consistent.
Put the two papers side by side and a simple picture appears. The slow pace is where the measurable change lives. In this one study, the device layered on top did not move the needle further.
That matters because much of the current “vagus nerve” marketing frames the breath as a weak, do-it-yourself version of a gadget. This small study hints that it may be the other way round, at least for the specific setup tested: the breathing is the main ingredient, and the gadget is optional.
The old version of the same idea
None of this is new to pranayama. Long before anyone wired an earpiece, yoga texts described practice as a slow, counted breath, with the out-breath often longer than the in-breath. Nadi shodhana, or anulom vilom, adds a second structure: in through one nostril, out through the other, then back. At a gentle count of five or six seconds each way, a round of nadi shodhana lands close to the six-breaths-a-minute pace the 2023 study used.
We are not claiming alternate nostril breathing does what the study measured. The paper did not test it. The honest link is simpler: the pace the study found sufficient on its own is a pace the old practice already asks for.
How to try the slow pace
- Sit upright in a chair or on a cushion. Let the shoulders drop.
- Breathe in through the left nostril for five or six seconds, closing the right with your thumb.
- Breathe out through the right for the same count.
- Breathe in through the right, then out through the left. That is one round.
- Do two or three rounds. No breath holds are needed at this stage.
Keep the breath soft enough that it makes almost no sound. If you feel dizzy or lightheaded, stop and breathe normally. If you have a heart or blood pressure condition, are pregnant, or have been told to avoid breathing exercises, check with your doctor first.
What to take from it
One small crossover study does not settle anything, and the authors say as much. Other stimulation settings could behave differently. But for anyone wondering whether they need a device to get the benefit of a slow breathing practice, this paper is a useful data point. Twenty-two people, two sessions, six breaths a minute, and the stimulator added nothing measurable.
The slow count was enough to see the effect in this study. It is free, it needs no battery, and it has been taught for centuries.
Sources
- Szulczewski MT, D’Agostini M, Van Diest I. Expiratory-gated transcutaneous auricular vagus nerve stimulation (taVNS) does not further augment heart rate variability during slow breathing at 0.1 Hz. Applied Psychophysiology and Biofeedback, 2023. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10412484/
- Laborde S, et al. Effects of voluntary slow breathing on heart rate and heart rate variability: a systematic review and a meta-analysis. Neuroscience and Biobehavioral Reviews, 2022. https://pure.solent.ac.uk/en/publications/effects-of-voluntary-slow-breathing-on-heart-rate-and-heart-rate-
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