Science moves on bodies of evidence

I’ve long made the point that science moves on bodies of evidence, not individual studies. If you don’t have repeatable data, then you don’t have much of anything. This is why the media is frequently so bad when it comes to reporting on recent studies; they report (or at least imply) individual study results as conclusions that are being made by the scientific community at-large. The truth is usually more like, one group of researchers found some interesting results.

And with that in mind, I turn to one of my favorite topics in science, circumcision. My numerous posts are easily searchable, so I won’t bother to link them, but for those who are unfamiliar with my stance, let me be clear: I am hugely in favor of circumcision because the science is in – circumcision saves lives. Furthermore, there is a very clear body of evidence that circumcision does not decrease sensitivity or sensation. In fact, a recent study found just the opposite:

Of 454 circumcised men, 362 (80%) returned for a follow-up visit 6 to 24 months after VMMC (voluntary medical male circumcision). Almost all (98%) were satisfied with the outcome of their VMMC; most (95%) reported that their female partners were satisfied with their circumcision. Two thirds (67%) reported enjoying sex more after VMMC and most were very satisfied or somewhat satisfied (94%) with sexual intercourse after VMMC. Sexual function improved and reported sex-induced coital injuries decreased significantly in most men after VMMC.

For someone like me who is greatly in favor of circumcision, this is great news. While it is only a survey study rather than a research study, it still provides evidence that circumcision is even better than the scientific community thought. However, that’s just not how science moves. Find me another several dozen studies like this using a variety of methods, and if they show a trend that confirms the results here, then I’ll start believing it. But as things stand now? I can’t make the leap. There is a standing body of evidence that says circumcision doesn’t affect sensitivity or sensation one way or the other; for every study that reports positive results, there’s one that reports negative results (and more often, studies report mixed or push results).

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One Response

  1. How I wish there were more skeptics like you Michael, who actually bother to look at the evidence on this topic, rather than just Googling up whatever intactivist BS triggers their confirmation bias. For some time now I have been trying to persuade UK skeptic Myles Power that his video on the topic (https://mylespower.co.uk/2014/07/14/the-science-of-circumcision-2/) gets it all wrong. He even parrots the 20000 nerves myth. Feel free to see if you can change his closed mind. Posts get ignored, maybe a private email from a fellow skeptic might help. I am disturbed by anti-circ nonsense penetrating the sceptical community, so it is great to see a real skeptic like you who has not fallen for it. And sad to see one like Myles Power who has.

    With respect to your latest post (bravo!), there is a whole body of evidence that circ makes no difference to sexual pleasure or function. The studies intactivists cite tend to be poor (e.g. self-selected convenience samples, prone to selection bias, as with the Frisch and Bronselaer studies) or with dodgy stats (Sorrells). Fortunately there are plenty of better studies to counter them with, like the recent British one: http://europepmc.org/articles/PMC4502984 And two randomized controlled trials (the so-called “gold standard” of epidemiology): pubmed/18086100 & pubmed/18761593. And a RCT on women (seems having a circ’d partner is no impediment to pleasure at their end of the organ): pubmed/19522862 (in fact they tended to think it was better!)

    When dealing with a large number of studies, of varying quality, and contradictory findings, the best approach is to conduct a review. There are objective methods of weeding out poor quality studies, and focusing on the better ones. When this is done something interesting happens. The studies intactivists love to cite disappear, and what remains consistently shows that circ has little or no effect. A recent extensive review by Morris & Krieger found exactly that: pubmed/23937309. Predictably intactivists dismiss it on ad hominem grounds (the authors are famously pro-circ). But that cannot be said of a subsequent review by Danish researchers which found the same: pubmed/27399981. Denmark is an anti-circ society. Likewise, the Chinese are a non-circumcising culture, so the ad hominem excuse cannot be deployed against their meta-analysis of the ten best studies, and which found no difference between circ’d & non-circ’d men in prevalence of a range of sexual dysfunctions: pubmed/23749001.

    These studies take two approaches. Each based on comparing circ’d & non-circ’d males. They are either RCTs (the best study-type) in which men are randomly assigned to be circ’d or not, then followed up two years later. Or they compare a group already circ’d (presumably as babies) with one not. Critics object that the former only look at men willing to be circ’d, and therefore who do not value their foreskins, thereby excluding any that do. But this cannot be said of the latter approach. That the two approaches consistently get the same result (circ has no adverse effect) undermines the objection about the RCTs only attracting men who don’t value their foreskins.

    Other approaches include objective sensitivity measurements. The infamous Sorrells study (pubmed/17378847) by intactivists (hardly impartial!) claims that the glans gets desensitised, and the tip of the foreskin is the most sensitive part. Critics found a bunch of problems with the stats (see the correspondence that followed – links are in Pubmed). Van Howe (who did the stats) later responded with a straw man (http://circfacts.org/sloppy-logic/#slog31 ) but the whole thing is a red herring anyway (http://circfacts.org/sloppy-logic/#slog29 ). Bossio did a much better study, she looked at fewer points, but at more sensation types. Circ made no difference: pubmed/26724395. Predictably intactivists replied with spurious objections which were rebutted (the link in Pubmed to Frisch is actually a whole bunch of letters ending with a reply by Bossio).

    Schober got men to rank the different parts of their organ by how erogenous they were. They put the glans first, foreskin last (pubmed/19245445 ) but the sample size was small (n = 11). But it fits the histology – what we know of the innervation of the penis indicates that the foreskin is irrelevant when it comes to sexual function and pleasure: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4498824/ And this is an extensive review of the topic.

    So we have multiple quality studies, using different approaches, by multiple researchers all over the world, on large samples, plus reviews and a meta-analysis, all pointing to the same thing: circumcision has no adverse effect on sexual function or pleasure. A substantial body of evidence!

    Please check out a new website I edit and contribute to: http://www.circfacts.org There is a whole section on penile sensitivity debunking common myths. I hope you will find it useful. Items are being added slowly (about one a month just now, it is hugely time-consuming) so do keep an eye on it. Meanwhile keep up your excellent work.

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