1. Angus MacAskill Angus MacAskill Canada says:

    I don't have access to the studies, but Dr Hedman's statements strike me as being too broad. A cross-sectional survey is inherently limited in what it can tell us about cause and effect. The data presented here would also be consistent with a scenario where the entire population of dual users was using e-cigs to gradually reduce their cigarette intake, on track to quitting completely.

    I don't claim that's the case for ALL dual-users, but it's surely true for SOME of them, and the study design is unable to capture this.

    Moreover, if you're going to make a claim about e-cigs' effectiveness for quitting, you can't just look at former smokers, you need to consider former vapers as well! Otherwise you're ignoring people who used e-cigs to help quit smoking, succeeded, and then quit vaping too.

    • Angus MacAskill Angus MacAskill Canada says:

      As for the question of respiratory problems, did the researchers attempt to control for frequency of smoking, or past smoking? If not, then they are probably seeing the effect of a confounding variable.

      Heavy smokers, long-term smokers, and smokers with trouble breathing are all more likely to try e-cigarettes as a substitute or a quitting aid, but to have trouble quitting completely. The same groups are likely more prone to experience a wheeze or cough, too. Taken together, this could explain why dual-users experience more frequent respiratory problems, but e-cigarettes are not the cause.

      The study author admits this possibility, but assigns it equal likelihood as a novel (and IMO unlikely) interaction between e-cigarettes and regular smoking. She then emphasizes that e-cigarettes "cannot be marketed as a safe alternative" to smoking.

      The author should have done the responsible thing and admitted that the study design does not allow her to make these kinds of statements.

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