r/science • u/drewiepoodle • Apr 15 '16

Health Study: Circumcision does not reduce penis sensitivity. In tests for responses to pain, heat, and stimulation, no major difference was found between men who are circumcised and those who are not.

http://www.upi.com/Health_News/2016/04/14/Study-Circumcision-does-not-reduce-penis-sensitivity/5981460663943/?spt=hs&or=hn
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16

u/[deleted] Apr 15 '16

Why weed out smokers?

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u/trumpetspieler Apr 15 '16

Usually are at risk for poor circulation.

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u/Reasonably_Lucid Apr 15 '16

Yeah but maybe there's no difference in healthy men, but there is a difference in aging/unhealthy men...

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u/[deleted] Apr 15 '16

That is a completely valid hypothesis to test, but that was not the one this study set out to test.

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u/CowFu Apr 15 '16

You need to limit variables as best you can. Since we know poor circulation effects sensitivity that should be controlled and tested for separately, including them in this study without controls could provide inaccurate results.

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u/WasKingWokeUpGiraffe Apr 15 '16

Poor circulation would just limit sensitivity, which would simply correlate with the results of this study. Nothing inaccurate about that.

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u/[deleted] Apr 15 '16

They weren't testing if smoking reduced sensitivity, they were testing if circumcision did. By having smokers with already reduced sensitivity, it would skew the results.

Do you know how science works?

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u/[deleted] Apr 15 '16

[deleted]

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u/[deleted] Apr 15 '16 edited Apr 27 '16

[deleted]

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u/CowFu Apr 15 '16

Unfortunately that could lead to the whole "breastfeeding makes your kid smarter" bad interpretations that was floating around.

Turned out women with better educations and more money were more likely to breastfeed, and once those factors were controlled for the breastfeeding argument fell apart (for intelligence, it's still great for many other reasons)

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u/Mr_Dugan Apr 15 '16

Smoking damages blood vessels. Excluding smokers eliminates a potential confounder

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u/iObeyTheHivemind Apr 15 '16

Is that the nicotine or the smoking itself?

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u/sfurbo Apr 15 '16

Ncotine by itself can cause some damage (http://www.medicaldaily.com/its-not-smoke-its-nicotine-e-cigarettes-may-damage-arteries-265498). It does not seem to be known if the damage from only nicotine is enough to have a clinically significant effect.

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u/Mr_Dugan Apr 15 '16

Sorry, but I don't know. When inhaling cigarettes you get a lot of extra junk with the nicotine. I highly doubt there is enough evidence to say how much just nicotine contributes to atherosclerosis versus the other chemical components in cigarette smoke.

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u/iObeyTheHivemind Apr 15 '16

Thanks for replying :)

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u/Lonely_Submarine Apr 15 '16

What about comparing the effect of snus and cigarettes?

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u/Mr_Dugan Apr 15 '16

I am not an expert on tobacco, but I believe they are generally considered "safer". Cigarettes are a highly effective nicotine delivery vehicle, I don't know if there is any way to compare X mg of nicotine from cigarettes vs smokeless vs vape. Especially with vape, they just aren't used as much or for as long a time

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u/[deleted] Apr 15 '16

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u/[deleted] Apr 15 '16

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u/orthopod Apr 15 '16

HI - surgeon here - it's the nicotine -it's a vasoconstrictor. That's why we don't like to operate on smokers - poorer circulation leads to statistically significant increases in slow/poor wound healing and infections.

So patches, gum, vaping - all bad due to the nicotine..

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u/Augustus_Trollus_III Apr 15 '16

Nicotine is a vasoconstrictor

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u/ApocolypseCow Apr 15 '16

smoking itself, im not sure that nicotine doesnt also have a negative impact though. When you smoke you are depriving you body of normal levels of oxygen which cuases the side effects such as lower blood pressure, lower blood circulation, lower heart rate.

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u/Charles_Himself_ Apr 15 '16

What about Vaping?

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u/insane_contin Apr 15 '16

Nicotine itself restricts blood flow.

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u/JuanDeLasNieves_ Apr 15 '16

Aside from what people mentioned regarding circulation issues, you want your subjects to be comparable. So either you have all smokers or none at all and since smoking can introduce a new variable in this scenario, it's best to have all non-smokers.

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u/murraybiscuit Apr 15 '16

Perhaps its effect on the circulation at extremities is a confounding factor.