Diet soda and stroke & dementia news coverage: 3 key points weren’t always reported

soda dementia stroke

The Framingham Heart Study group will turn 70 next year. That’s given them enough time to start studying the offspring of their original study cohort — which they have done since 1971 —  as well as know how to cautiously present results from their bread-and-butter: long-term observational studies.

Which is what they do with a study released this week in the American Heart Association’s journal, Stroke.

The findings? Drinking at least one artificially sweetened beverage daily was associated with an increased risk of developing stroke or dementia compared to those who drank these beverages less than once a week.

The news release headline is accurate and cautious:

“Diet drinks and possible association with stroke and dementia; current science suggests need for more research”

And right out of the gates, in the second paragraph, they quickly highlight:

“The authors caution that the long-term observational study was not designed or able to prove cause and effect, and only shows a trend among one group of people.”

I asked Preeti Malani, MD, an associate editor at JAMA, and one of our editorial contributors, what she thinks of the press release.

“In general , I agree that the release is quite good and does try to highlight limitations of this observational study,” says Malani, a former journalist herself. “One potential issue is the presentation of relative risk (‘three times the risk’) at the top. Even if a risk is ‘three times higher’ the absolute risk is likely quite low. That’s one thing all press releases should include if those numbers are available. A quote from one of the authors does this, but you have to read down toward the end of the release.”

And here is that quote from the news release by co-author Matthew Pase, MD:

“In our study three percent of the people had a new stroke and five percent developed dementia, so we’re still talking about a small number of people developing either stroke or dementia.”

The news release also does well to highlight some of the limitations of the study, appropriate considerations when comparing sugar-sweetened and artificially sweetened drinks, as well as important related concerns with regard to obesity and diabetes.

How did reporters handle this?

It was inevitable that this study would get heavy news coverage, especially in the United States where we drink over 40 gallons of soda per person, per year. That makes covering this story carefully all the more vital.

But that’s not what happened.

Other than reporting the basic design and findings of this study, adequate reporting of the Framingham findings would need to make three caveats quite clear. First, that association does not imply causality. Second, absolute risk numbers need to be included to place the relative risk in context. Finally, the limitations of the study are not trivial and should be explained.

Most coverage made it clear that the association between artificially sweetened drinks and stroke and dementia did not imply causality. That this was well reported may be attributable to not just the carefully written press release, but also to the authors who clearly made an effort of bringing this up in most interviews.

But very few stories – the USA Today and WebMD are two examples — provided the absolute risk numbers. It may be that relative risk makes for better headlines while absolute numbers have less punch.

Likewise, the limitations of this study — which were very clearly laid out out in both the published study and the news release — were rarely mentioned. It wouldn’t have taken much extra effort for reporters to simply mention that most Framingham studies are hard to generalize to the public at large because, not only are they observational, but because they under-represent ethnic minorities. Also, this study relied upon a food questionnaire that required participants to look back quite a few years. Recall bias is a major concern.

I only found one reporter who covered all three caveats. That was Alexandria Bachert in her article in MedPage Today. This is hardly a mainstream news outlet … but I wish it were.

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