Kevin Lomangino is the managing editor of HealthNewsReview.org. He tweets as @Klomangino.
If only Yale University PR folks had spent some time with our toolkit of resources.
If they had, it’s hard to imagine they would have sent out this misleading tweet last week about the benefits of aspirin for pancreatic cancer prevention:
— Yale University (@Yale) January 10, 2017
We recently updated our primer titled “Reporting the findings: Absolute vs relative risk” and I hope Yale will take a look at it.
This practical, hands-on guide says, “It’s wise for you to be skeptical and ask ‘of what?’ anytime you hear an effect size of 20-30-40-50% or more. 50% of what? That’s how you get to the absolute truth.”
In this case, because pancreatic cancer is relatively rare, the impressive-sounding 50% reduction doesn’t amount to very much. According to the American Cancer Society, a 60-year-old man has a 0.41% (1 in 241) chance of developing pancreatic cancer during the next ten years. (Risk varies greatly with age and is much lower at younger ages.) So cutting that risk in half might bring it down to about 0.2% (1 in 480).
It’s a 50% drop, sure, but the risk was already very small to begin with. In this case, it’s more helpful to news and health care consumers to describe it as a 0.2 percentage point reduction.
And then there are the harms of regular aspirin use; the Yale news release that the tweet links to doesn’t mention any. But taking aspirin regularly isn’t a harmless intervention — far from it. It’s well known that taking aspirin every day can cause serious bleeding in the gastrointestinal system and, less frequently, in the brain. That’s why guidelines for aspirin use in cardiovascular disease prevention don’t recommend it for people at low risk of a heart attack. The potential benefits may be outweighed by the risks of a serious bleed.
At an even more basic level, the tweet, the news release, and even the study that they are all based on misreport the nature of the evidence. They confuse association with causation — an issue that we also address in our toolkit in the primer titled Observational studies: Does the language fit the evidence? Association vs. causation.
The study abstract states: “Regular use of aspirin thus appears to reduce risk of pancreatic cancer by almost half.” And throughout its promotional materials, Yale frames the results as showing that aspirin “lowered” the risk of pancreatic cancer.
Both of these statements represent a leap that’s not supported by the evidence.
Its own conclusions notwithstanding, the study, which was observational in nature, only showed an association between aspirin use and pancreatic cancer — not that one caused the other. Our primer explains the problem of drawing cause-and-effect conclusions from observational studies:
Because observational studies are not randomized, they cannot control for all of the other inevitable, often unmeasurable, exposures or factors that may actually be causing the results. Thus, any “link” between cause and effect in observational studies is speculative at best.
In reporting on observational research, language here is crucial, because the audience may not be familiar enough with epidemiologic evidence and study design to appreciate the nuances.
Yale happened to trip our radar on this study because of its sensational tweet. But to be fair, the American Association of Cancer Research, whose journal Cancer Epidemiology, Biomarkers & Prevention published the findings in December, made many of the same misleading statements in its release plugging the same study in December of last year. That release was headlined “Regular Aspirin Use May Reduce Risk for Pancreatic Cancer.”
But the AACR at least took some steps to rein in the unbalanced framing evident in the Yale release. For example, it quotes a researcher describing pancreatic cancer as “relatively rare” and noting that “regular aspirin use can cause appreciable complications for some. Therefore, a person should consult his or her doctor about aspirin use.”
That was context missing in Yale’s release, which told readers that pancreatic cancer is “especially lethal” but didn’t note its rarity. Yale did mention at the very end that the study “had limitations, most notably that it relied on participants accurately self-reporting past aspirin use.”
I don’t know for certain what effect these incomplete messages might have on the general public, but I don’t think they’re helping.
In the best case scenario, someone who’s already taking regular aspirin for cardiovascular disease prevention might learn of an added, speculative benefit of that strategy — very small in size — that’s a long way from being proven.
Worst case, someone not currently taking aspirin might conclude from these misleading materials that regular aspirin is something they should start taking to prevent pancreatic cancer.
That would be unfortunate because no evidence-oriented doctor would recommend this. The research is still preliminary and the established harms outweigh the uncertain benefits.
If my criticism seems harsh, it’s because this isn’t the first time that we’ve called out Yale for misleading messages that have the potential to do harm — witness the myeloma “discovery” that wasn’t.
Institutions as prestigious as Yale University should be setting the standard for accurate PR communication that informs and doesn’t mislead..