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CNN claims aspirin can reduce cancer death risk, falling into observational study trap


2 Star


Low-dose aspirin can reduce risk of death from cancer, research says

Our Review Summary

This story is a brief, uncritical look at a study examining ties between aspirin use and rates of cancer mortality.

The headline overstates what the observational study was capable of measuring. It states “Low-dose aspirin can reduce risk of death from cancer, research says.” That’s incorrect–all that we know from the study is that aspirin use was associated with a reduced risk of death from several cancers. The study wasn’t capable of proving that aspirin “can reduce” cancer death risks. (This is a common problem we see in news coverage.) This framing is echoed throughout the story, unfortunately.

That said, we were glad to see the story discuss some of the risks of taking aspirin and advising people to talk to their doctors first.


Why This Matters

Aspirin is ubiquitous and so is cancer. If readers see stories emphatically stating that aspirin “can reduce the risk” of dying from cancer, many readers may act upon that news–unaware that the research wasn’t capable of proving this benefit.


Does the story adequately discuss the costs of the intervention?

Not Applicable

There are no costs discussed in this story, however, aspirin is ubiquitous and very inexpensive.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The story states the percentages of reduction of cancer among aspirin users as opposed to those who do not take aspirin and divides the results by men and women. This is a good start, but readers deserve to see the actual numbers–known as the absolute risk reduction–along with the relative percentages.

Does the story adequately explain/quantify the harms of the intervention?


The story states “Not everyone can take aspirin, particularly if you are at high risk for ulcers and gastrointestinal bleeding. Studies have showed an increased risk of both when taking a daily aspirin.”

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

There is not sufficient information in the story to judge the quality of evidence. The two studies referenced in the story are well-known and generally well regarded as long-term observational studies, but the story does not really say anything about the studies’ design, the limitations, etc.

Why this matters: Results from studies such as these have misled clinicians and the public for decades. They are observational and subject to selection bias. For example, people taking aspirin (and hormone replacement therapy, and antioxidant vitamins) are more health conscious than those who do not. In those cases, it took different, more rigorous studies for clinicians to realize that hormone replacement therapy was harmful and vitamins were useless.

In this case, we know from randomized trials that cancer screening reduces colorectal cancer mortality. Without knowing whether results were adjusted for screening (and other risks such as family history, long-standing inflammatory bowel disease, etc.) the benefit of aspirin remains uncertain. Aspirin use also was determined by self-report on periodically administered surveys, and self-reporting can be inaccurate.

This HealthDay story, meanwhile, is an example of limitations being discussed.

…the findings can only point to correlations. “It’s always possible that aspirin use is a surrogate for a healthy lifestyle, in general,” he said.

And, considering the study findings have not been published, the HealthDay story also added this important detail:

The results should be considered preliminary until published in a peer-reviewed medical journal.

Does the story commit disease-mongering?


Cancer is a major cause of death in the U.S., and this story doesn’t disease monger.

Does the story use independent sources and identify conflicts of interest?

Not Satisfactory

There are no independent sources in this story.

Does the story compare the new approach with existing alternatives?

Not Satisfactory

No alternative approaches are included in this story. Cancer screening and lifestyle changes could have been included, for example, as evidence-based methods for lowering death risks of some types of cancer.

Does the story establish the true novelty of the approach?

Not Satisfactory

The story doesn’t clearly establish what’s new about this research–how, exactly, does it add to what’s already known about aspirin and cancer risk?

The news release indicates the novel finding is this: “These findings suggest that aspirin’s established benefits in cardiovascular disease and colorectal cancer reduction may extend to other common causes of death, including several major cancers.”

Does the story appear to rely solely or largely on a news release?


This story is similar to the news release, yet it does contain several quotes from the lead researcher that were not found in the news release. This earns it a barely passing satisfactory.

Total Score: 3 of 8 Satisfactory


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