I have noticed that Chinese massage seems to be becoming popular, and seemingly with it Traditional Chinese Medicine (TCM1). At least browsing through two of the larger shopping centres in Hamilton (bring on the hick jokes) I saw massage centres offering these services. In particular cupping was advertised. But what exactly is cupping2?

As with many modalities in TCM Cupping appears to be based on pre-scientific notions of blood stagnation and energy blockages3. Applying cups with a slight vacuum to the skin is meant to draw out the “toxins” which then results in improved health, somehow.

The active part of cupping essentially boils down to a pressure difference. The pressure is lower on the inside of the cup and greater on the outside, this difference causes the skin to be forced up into the cup4. This process in turn causes blood to gather in the region and may cause minor damage to the area resulting in bruising.

Presumably the fact that the skin appears to be drawn up into the cup gives the impression that there is a general pulling action at work here and that toxins and other “bad stuff” are pulled out of the body in this fashion.

The trouble with this is that pressure difference is a fairly crude physical process and with regard to this biological system lacks what we in the science biz call “Specificity”5. What this means is that there is no way for the cup to restrict the “pulling action” to only harmful chemicals (the “toxins”, say) and allow everything else to be unaffected, i.e. it is not “specific” to toxins. Everything will be drawn up in the same way.

In which case you get a lovely bruise and feel like you’ve done something but that’s about it.

Ok, that’s fine for just thinking about it. What about evidence, we’re always going on about evidence here.

I attempted to find a Cochrane review on cupping but while one was listed for pain relief there did not seem to be a completed review for perusal. I did come across this review that found equivocal results for the effectiveness of cupping for pain.

The review comments on the putative mechanism of cupping:

“Assuming that cupping was beneficial for the management of pain conditions, its mechanisms of action may be of interest. The postulated modes of actions include the interruption of blood circulation and congestion as well as stopping the inflammatory extravasations (escaping of bodily fluids such as blood) from the tissues. Others have postulated that cupping could affect the autonomic nervous system and help to reduce pain . None of these theories are, however, currently established in a scientific sense.” [Emphasis added, citations removed]

The discussion of the reviews limitations is especially worth noting:

“Our review has a number of important limitations. Although strong efforts were made to retrieve all RCTs on the subject, we cannot be absolutely certain that we succeeded. Moreover, selective publishing and reporting are other major causes for bias, which have to be considered. It is conceivable that several negative RCTs remained unpublished and thus distorted the overall picture. Most of the included RCTs that reported positive results come from China, a country which has been shown to produce no negative results. Further limitations include the paucity and the often suboptimal methodological quality of the primary data. One should note, however, that design features such as placebo or blinding are difficult to incorporate in studies of cupping and that research funds are scarce. These are factors that influence both the quality and the quantity of research. In total, these factors limit the conclusiveness of this systematic review.

In conclusion, the results of our systematic review provide some suggestive evidence for the effectiveness of cupping in the management of pain conditions. However, the total number of RCTs included in the analysis and the methodological quality were too low to draw firm conclusions. Future RCTs seem warranted but must overcome the methodological shortcomings of the existing evidence.”

In conclusion then, you may see a placebo effect from this treatment – though I suspect this is over rated as a therapeutic outcome6. You may also find yourself covered in bruises (though I hear they are painless – think of them as CAM hickies). So… Dubious premise with dubious benefit, same thing – different day.

Here are a couple of images for you to keep in mind…

Mmmmm, cupping goodness.

[UPDATE 30/5/12: Islam appears to support cupping, check out this completely unbiased arabic wikipedia article]

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Footnotes:

1. Can’t get away from TLAs

2. So many jokes spring to mind, I mean come on – “cupping”?

3. See this link for some scary science illiteracy around cupping. And here’s good old Wikipedia. And “blood stagnation” really? isn’t that gangrene or septicaemia or something?

4. Keeping in mind that a vacuum does not suck, high pressure pushes.  If I may geek out a bit here; hence one of my favourite exchanges from ST:TNG:

“You were right. Somebody blew out the hatch. They were all sucked out into space.”
“Correction, sir, that’s blown out.”
“Thank you, Data.”
“A common mistake, sir.”

– Riker and Data get precise about the physics of rapid decompression into the vacuum of space

5. Yeah, I know, it sounds made up.

6. See here, here and here.

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