I shuddered as soon as I read the BMJ news release headline, which read: “Estimated risk of breast cancer increases as red meat intake increases.“ I shuddered because I predicted to myself that many headlines, if not complete news stories, would report this as proof of cause and effect. Or, at the very least, caveats about association ≠ causation would be missing.
Call it splitting hairs if you wish. But the wording matters. And the wording of the BMJ news release – in my opinion – can easily mislead one into thinking that the study in question made a causal link – not just a statistical association. Let me break it down. The release – in short – stated that increased red meat intake increases breast cancer risk. “Increases risk” is a statement of causation.
Did it mislead journalists? I can’t prove that. I’m quick to say I can’t establish cause-and-effect. But I will suggest there may have been an association between the BMJ news release and stories headlined like this:
Medical News Today: Could red meat consumption increase breast cancer risk? (This is the old “question mark” form of journalism that Jon Stewart has mocked on the Daily Show.)
In this case, if you don’t understand observational studies, or you don’t understand what “association ≠ causation” means, and you have a major medical journal’s news release using causal language….but you’re still confused or uncertain…you just ask a provocative question, slap on the question mark at the end, and you’re safe.
KARE-11, the NBC station in Minneapolis-St. Paul, had no such uncertainty. They made it a statement of fact, headlining: “Study: Red meat intake could increase breast cancer.” (Thereby answering Medical News Today’s question, “Could it?”
Fox News in Philadelphia stated, “Red meat may raise breast cancer risk.” Yes, Fox/Philly, it may. But then again it may not.
The Daily Express in the UK made a statement of fact: “Red meat raises the risk of breast cancer by a quarter.“ Nope. That’s inaccurate. Raises risk implies proof of causation.
The UK’s Daily Mail reported: “Three bacon rashers a day raises breast cancer risk for young women.” Huh? Where did that come from?
Nature World News reported: “Red Meat Ups Breast Cancer Risk.” Nope. Statistical association, not causation. “Ups risk” implies cause and effect.
There were many other examples of stories that inappropriately used causal language to describe the study in question.
The Behind the Headlines service in the UK did its usual fine job explaining the evidence, stating at the end: “it should not be concluded from this particular study alone that red meat and processed meat increase the risk of breast cancer.”
And I was pleased to see that at least one news organization – there may been others – explicitly addressed my pet peeve. The Guardian quoted a cancer epidemiologist who said, “association does not necessarily imply causation.”
There you have it. 6 little words. That’s all I was looking for. The rest of the BMJ news release was OK; in fact, it mentioned association four times. But it never gave the 6 words that journalists – and the public – need to hear about such observational studies.
The BMJ could have included those 6 little words and perhaps helped avoid all of the misreporting – and certainly avoided another one of my rants against their news releases. Past rants:
Please, all offending parties, if you haven’t done so already, please read our primer: “Does The Language Fit The Evidence? – Association Versus Causation.“
The words matter. Public comprehension of research matters. Avoiding public confusion matters.
And none of this is to suggest that the observational study in question wasn’t important. It is important work. It may point to a strong statistical association- and that alone may be enough to guide public recommendations. But it is simply wrong to use causal verbs to imply that this one study established cause-and-effect. Journalists should care about that point of accuracy. The public should care. And journals that publish news releases should care.
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