August 20, 2013

Scary coffee stories – add cream and two lumps of caveats

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Put Down That Coffee. It Might Be Killing You.

That was an actual headline from a story the other day about a paper published online first by Mayo Clinic Proceedings pointing to an association – not proof of cause – between heavy coffee consumption (>28 cups a week) and higher death rate in people younger than 55.

Other headlines:

New study: Coffee can kill you – Atlanta Magazine

Drinking More Than Four Cups of Coffee A Day Raises the Risk of an Earlier Death (Business Insider story on San Francisco Chronicle website)

Four Cups of Coffee a Day Means Higher Death Risk – UPI story on HispanicBusiness.com

No it can’t…no it doesn’t…and no it doesn’t. At least there is no proof of “raising the risk of an earlier death” from the study in question. The researchers reported a “positive (statistical) association.” That’s not causation. So causal phrases such as “raises risk” or “can kill you” are unfounded. I always have to remind first-time readers that I’m not knocking the potential importance of observational studies. They are what they are and they ain’t what they ain’t.

At last check there were more than 170 stories about this study that turned up on a simple web search.

One of the study authors, in this video, explains that another of the team’s papers in another journal points to benefits or protective effects of coffee consumption. But that was a point that didn’t make it into many stories.

USA Today reported:

“Gregg Fonarow, co-chief of clinical cardiology at the David Geffen School of Medicine at UCLA, says, “Differences in other dietary factors, marital status and other socioeconomic factors that were not adjusted for in this study may account for some or all of these observations.”

Fonarow, who was not involved in this research, says observational studies that survey people about their coffee intake and tie that to how many died from any cause have yielded mixed results.

Consider a 2012 study that found that coffee drinkers ages 50-71 had a lower risk of death than their peers who did not consume coffee. In that study, researchers from the National Cancer Institute, part of the National Institutes of Health, and AARP found that the more coffee consumed, the more a person’s death risk declined.”

Look what happens when you make another phone call and involve another – independent – expert voice to scrutinize the evidence.

Coffee causation stories are getting stale with us. Just check out some past posts:

May 2010 – CBS is wrong on coffee “lowering risk” of uterine cancer

June 2010 – Wisdom of the crowds: news consumers tired of misinterpreted observational studies

February 2011 – Why would the Wall Street Journal post this Fox News video on coffee as cure & killer?

March 2011 – Coffee & stroke: what the study didn’t prove and what some stories got wrong

May 2011 – Story whips up confusion over coffee and breast cancer risk – hurts more than helps

October 2011 – Another day, another slew of misleading media messages on observational study

May 2011 – Coffee & prostate cancer: Some news reports got it right. Others.

May 2012 – Another coffee observational study – another round of misplaced emphasis

June 2012 – Coffee clichés and the tired old trend on observational study stories

July 2012 – As long as news keeps cranking coffee benefit stories, we’ll keep commenting on them

December 2012 – Please, Grey Lady, don’t spill more coffee observational studies on us

Anyone who wants to learn more about why the language matters in such stories should read our primer, “Does The Language Fit the Evidence? Association Versus Causation.”

ADDENDUM ON AUGUST 22: See Evelyn Lamb’s post, “Sex Makes You Rich? Why We Keep Saying ‘Correlation Is Not Causation.’ ”

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