Does Vaping Cause Bone Damage? Yes and No, a Confusing Study Claims

"The evidence against vaping is mounting, and a new study now links e-cigarettes with an increased risk for broken bones," a recent MSN headline claimed, based on the results of a study just published in the American Journal of Medicine Open. Like so many adverse effects allegedly linked to e-cigarettes, their supposed impact on bone health is speculative at best. We can see why by comparing what the media said about the research to what the paper actually reported.

According to the press release, the researchers studied a sample of more than 5,500 American adults. There were 4,519 (81.2%) never e-cigarette users in the sample, 1,050 (18.8%) ever e-cigarette users, and 444 (8.0%) with fragility fractures. All the numbers were reported in 2017-2018 as part of the National Health and Nutrition Examination Survey (NHANES).

Conclusion:

Results showed a higher prevalence of fragility fractures among e-cigarette users compared to non-users. Researchers also found that individuals who used both conventional and e-cigarettes had a higher prevalence of fragility fractures compared to conventional smokers alone.

First issue: it's been widely documented that vaping is far less harmful than smoking, perhaps as much as 95 percent less. In light of this information, it's not clear why dual-use, which almost always reduces the number of cigarettes a smoker consumes, would negatively impact bone health more than traditional smoking.

Moreover, current vapers had a lower prevalence of fractures than former vapers. “[W]e observed a non-significant association between current e-cigarette use and fragility fractures,” the researchers wrote, “whereas former e-cigarette use was significantly associated with fragility fractures.” If vaping is the problem, surely no longer vaping leads to better outcomes. Yet, that's not what the study found.

Fuzzy definitions

As we've seen with previous vaping research, the authors defined “vaping” and “smoking” in terms so broad that the definitions were essentially useless. I suspect that's why their results make very little sense. Study participants were classified as current vapers if they had vaped at least once at any point in their lives and once in the last 30 days. That would include someone like me, who uses an e-cigarette multiple times daily, as well as someone who vapes once a month. Anyone who had smoked at least 100 cigarettes in their entire life was classified as an “ever smoker.” Of these individuals, participants who answered yes to “Do you now smoke cigarettes?” were categorized as “current smoker.”

The problem with these definitions is that individuals in the same category have wildly different exposures. Someone who smokes, say, a pack of cigarettes a month is exposed to far fewer harmful chemicals than a person who smokes two packs a day. The same principle applies to e-cigarettes. An e-cigarette user ("vaper") who vapes once a month is not exposed to nearly as much propylene glycol and vegetable glycerin (VG), common ingredients in e-cigarette liquid, as I am.

If vaping is a risk factor for osteoporosis—and that's a giant “if” at the moment—the study's definition of “current users” offers no clinically useful data. It's like saying consumers who eat one serving of French fries a month or 100 servings over the same period are “current potato users” and have an elevated risk of Type 2 Diabetes. We know that's an absurd association, yet tobacco researchers regularly try to establish the same kinds of links between vaping and adverse health outcomes.

Serious limitations

The researchers came close to acknowledging this limitation, writing that “granular characteristics of e-cigarette use such as brand of e-cigarette used, duration of vaping were not systematically available to allow for such sub-group analyses.” Good on them for saying as much, but why not just do a better study that would allow them to answer those questions? Here are two more key details from the study's limitation section:

Also, there is the possibility that for some individuals e-cigarette use may have started after fracture occurrence and diagnosis. Furthermore, this study did not analyze the relationship between current e cig users who were former conventional cigarettes users and the rates of fragility fractures. Doing so might have opened up a wider reach of clinical implications.

If participants began vaping after they had fractures, then vaping obviously didn't cause the fractures. The last sentence in the quoted paragraph is pleasantly vague, but a “wider reach of clinical implications” could mean that current vapers have an increased fracture risk than non-smokers because they smoked combustible cigarettes for many years. Tobacco use is, of course, a well-known risk factor for osteoporosis. But we can't address these possibilities given the limited data included in the study.

The researchers claimed that the “potential public health implications of our findings are telling.” With due respect, drawing any conclusions from this research would be a mistake. It's certainly possible that chronic vaping could cause bone damage, but we need better-designed studies to uncover that relationship, should it even exist.