Do Studies Show Vaping Causes Cancer? No.

In February 2022, the World Journal of Oncology published an article by a team of 13 researchers claiming that vapers are about as likely to get cancer as people who smoke traditional cigarettes.

Citing this article, Stanton Glantz, a tobacco-control activist and retired professor of medicine at the University of California, San Francisco, claimed that not only are there “some carcinogens in e-cigarette aerosol,” but “now there is also direct evidence that people who use e-cigarettes are at increased risk of some cancers.”

And then the World Journal of Oncology‘s editors retracted the study because “concerns have been raised regarding the article’s methodology, source data processing including statistical analysis, and reliability of conclusions.”

The study is indeed riddled with errors. One section, for example, says 2.3 percent of cancer patients in the study vaped and 16.8 percent smoked traditional cigarettes, while the table cited in that passage showed 1 percent of cancer patients in the study vaped and 46.1 percent smoked traditional cigarettes.

As Reason‘s Jacob Sullum has noted, the retracted study also suffered from another basic flaw, shared by other studies that weren’t retracted but probably should have been: It doesn’t take into account when its subjects started vaping versus when they were diagnosed. An analysis in Internal and Emergency Medicine cited 11 studies with this problem. As Sullum notes, this is also the reason that a 2020 study claiming to show that vaping causes heart attacks was retracted.

These studies use large observational databases to see if vapers are more likely to have health problems than nonvapers. Although the National Center for Health Statistics claims that the data are representative of the overall population, they’re actually not well-suited to studies of this sort. The data are based on self-reports that are often wrong and may contain missing or inconsistent entries. Important information wasn’t collected. The databases are not random population samples because only about half the invited subjects agreed to participate and it’s likely that certain groups are over- or underrepresented because ​​they face different incentives when deciding whether or not to sign on.

The retracted study claimed a large sample size with data on 154,856 subjects. For assessing the cancer risk of vaping versus traditional smoking, what we should be looking at are vapers who never smoked traditional cigarettes, yet have cancer. There were 180 vapers with cancer in the study. But based on general population percentages, probably fewer than 100 had never smoked traditional cigarettes. That’s too small a sample to draw robust conclusions. The median age of vapers in the study was 25, versus 62 for traditional smokers, and they had very different breakdowns of income, race, sex, and medical conditions. Adjusting for all these factors would require a minimum of 1,000 observations.

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