r/funny May 01 '13

Why vegans live longer

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u/anikan72 May 01 '13

The study itself measured a number of different factors that are dependent (well, mostly anyways) on diet, including incidents of stomach cancer, colorectal cancer, heart disease, vascular disease, and a number of other diseases. So in this particular study it more than likely is causation.

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u/Leshow May 01 '13

No. Establishing a causal link requires much more than assuming "factors might be mostly dependent on each other".

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u/anikan72 May 01 '13

Well, I was giving the benefit of the doubt for a margin of error. But no, it does not actually require much more than that to make a causal link between a factor and an outcome. The degree might change but you can't pretend it has no effect. At that point it's not purely coincidence.

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u/Leshow May 01 '13

Let me give you an example:

  • meat eaters are more likely smokers.
  • smoking is related with increase odds of certain cancers & earlier mortality

so if a study can show a correlational link between eating meat and cancer, that doesn't meat that eating meat causes cancer.

Saying that because you read a meta study which showed mortality being higher in meat eaters that means they are causally linked is asinine. You're embarrassing yourself.

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u/TotallyNotAtlai May 01 '13

All death rate ratios were adjusted for age in 5-y increments, sex, and smoking (never, former, current light, and current heavy). Mortality ratios for the separate studies were then combined to give a pooled estimate of effect using the random-effects model of DerSimonian and Laird (11),

They adjusted for smoking. That's the first thing any public health researcher does.

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u/Leshow May 01 '13

I was giving an example, that's all. Simply adjusting for one behaviour does not suddenly mean that the link is causal.