How Brizzy looks at the evidence
The same breath can be well studied for one effect and barely studied for another.
Brizzy reads the research for one effect, then says how solid that conclusion is. The label is a plain word. It is there so you can see the state of the research, not so we can talk you into a practice.
Every effect has its own research story
A breathing technique is not simply proven or unproven. The research for a calmer body can be much stronger than the research for better sleep, even when the breath is the same.
So the evidence level belongs to the effect, not to the technique as a whole. One practice can carry a Strong label for one effect and an Insufficient label for another. That is not a contradiction. The studies asked different questions.
The four Evidence levels
These four words are the whole public scale. Each one answers a single question: how solid is the research conclusion for this specific effect?
Solid research support. Several well-designed studies show similar results, with few major uncertainties.
Slow breathing for heart-rate variability is Strong because a meta-analysis of 223 studies finds a consistent result: heart-rate variability rises during the practice. [1]1
Good evidence, with some gaps. Research supports this effect, but some important questions remain.
Cyclic Sighing is Moderate for a calmer body, scoped to the resting-breathing finding. The walk-through below is only that finding. Mood in the same trial is less certain and does not take this rating.
Some evidence, but not enough yet. Some studies support this effect, but the research is still limited or mixed.
Oxygen Wave for energy is an example of Limited evidence.
We don't know yet. There isn't enough reliable research to tell yet. That doesn't mean the effect isn't real.
Box Breathing for focus is an example of Insufficient evidence.
What we look at
Four considerations, read together. None of them is a step that has to come first, and none of them is worth a fixed number of points. We do not add them into a score. There is no hidden weighting formula.
The approach is built around established evidence-appraisal principles. It is not a formal GRADE rating, and it is not the Oxford scale.
Study quality
How well was the research designed and carried out?
Amount of evidence
How much research is there, and how many people were studied?
Consistency
Do different studies find similar results?
Relevance
Did the studies actually test this breathing practice and this effect?
A careful trial of a different practice, or of a different outcome, does not automatically transfer. Relevance is what keeps a strong result from being borrowed by a claim the studies never tested.
Evidence level and research finding are different
The level tells you how solid the conclusion is. It does not tell you what the conclusion says.
The research may show that an effect is supported. It may show that no meaningful effect was found, or that studies point against a claim. It may show that the claim has not been properly tested, or that the claim is not a well-defined scientific question. Those are findings. The evidence level is how much weight that finding can bear.
Several reasonably good studies can agree, and what they agree on can be that nothing meaningful showed up. That can be a Moderate conclusion. Moderate does not mean the effect was medium-sized.
A negative result is still a result. When the studies are good enough, and they point the same way, the conclusion that an effect was not found can be Moderate. It does not have to be pushed down the scale just because the news is disappointing.
The same split works at another level. No meaningful difference can be a Limited conclusion when the research behind it is still thin. The level does not change what the finding says.
What Insufficient really means
Insufficient means there is not enough reliable evidence to tell whether this effect occurs.
It is not proof that something does not work. It is not a negative rating under another name. And it does not mean the effect is probably real and science has simply not caught up. We do not know yet. That is the whole claim.
Where tradition fits
Some breathing practices have been used for generations, or are widely practised today. Brizzy may describe these as traditional practices. Tradition itself is not scientific evidence. It is also not a reason to wave a practice away.
A traditional practice can have Strong, Moderate, Limited, or Insufficient evidence for a particular effect. The history and the research answer different questions. We keep them separate.
A real example: Cyclic Sighing
Cyclic Sighing is Moderate for resting breathing. The rating covers the resting-breathing finding in the trial below. The mood finding from that same trial is less certain, and it does not inherit this Moderate rating. Here is how the four considerations read for the resting-breathing effect.
| Consideration | For resting breathing |
|---|---|
| Study quality | Randomized trial |
| Amount of evidence | 1 trial · 30 participants |
| Consistency | Main finding not yet replicated |
| Relevance | Directly tested |
The 30 participants are the people randomized to the Cyclic Sighing arm. The trial randomized 108 people across four arms.
Why Moderate, not Strong?
The evidence still rests mainly on one trial, with no independent replication yet. That is a real gap, so the level stays Moderate.
The rating tells you how solid the research is, not how big the effect will be, and not whether you personally will feel it.
Evidence changes
A rating reflects the published research available at the time of review. A new study, a replication, or a result that disagrees can move the level. When the research changes, the label can change with it.
The word on the practice is our best reading of the public evidence for that effect, today. It is not a promise, and it is not a permanent stamp.
FAQ
Does Strong mean the effect will be large?
No. The evidence level tells you how reliable the conclusion is, not how large the effect is.
Does Insufficient mean the effect does not exist?
No. It means there is not enough reliable research to reach a conclusion. It is not proof that the effect is absent.
Does a traditional practice automatically get a higher evidence level?
No. Tradition describes long-standing or widespread use. It is separate from the evidence level, so a traditional practice can still be Strong, Moderate, Limited, or Insufficient.
Can Moderate mean that no effect was found?
Yes. If reasonably reliable research supports a conclusion of no meaningful effect, that conclusion itself can have Moderate evidence.
References
- Laborde S, Allen MS, Borges U, 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. 138:104711. (2022)
- Balban MY, Neri E, Kogon MM, Weed L, Nouriani B, Jo B, Holl G, Zeitzer JM, Spiegel D, Huberman AD. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine. 4(1):100895. (2023)