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The paper, “Potential deaths averted in USA by replacing cigarettes with e-cigarettes” by David Levy et al. published in Tobacco Control on October 2, 2017, attracted a moderate amount of attention with its conclusion that “Compared with the Status Quo, replacement of cigarette by e-cigarette use over a 10-year period yields 6.6 million fewer premature deaths with 86.7 million fewer life years lost in the Optimistic Scenario. … Our projections show that a strategy of replacing cigarette smoking with vaping would yield substantial life year gains, …”
This is a pretty impressive result until you consider that the Optimistic Scenario is based on a series of assumptions that are of which are inconsistent with empirical evidence to date:
Cigarette smoking prevalence drops from 17% to 5% in 10 years (from 19.3% to 4.6% in men and from $14.1% to 4.6% in women between 2016 and 2026).
The existence of e-cigarettes does not, on average, depress quitting cigarettes.
There is no relapse from e-cigarette use to cigarette smoking.
No youth who initiate with e-cigarettes progress to cigarette use.
No dual use of cigarettes and e-cigarettes.
The evidence free claim that e-cigarettes are 5% as dangerous as cigarettes.
(These assumptions were not clearly stated in the main paper; we figured them out based on the appendix and by examining the Excel spreadsheet of the model that the authors s...
(These assumptions were not clearly stated in the main paper; we figured them out based on the appendix and by examining the Excel spreadsheet of the model that the authors shared with us in response to an email. Their Pessimistic Scenario is based on similar assumptions, albeit with a higher e-cig risk.)
It is important to recognize that the authors don’t even pretend that their estimates are based on reality. In their Discussion they state: “Unlike previous models of e-cigarette use, our model was not developed to predict future e-cigarette and cigarette use based on past trends. Rather the aim was to examine a hypothetical endgame strategy of reducing cigarette use through switching to e-cigarettes. ”
I used their model to investigate the lives saved if cigarette use dropped along the same trajectory that the authors assumed because of increased smokefree laws, anti-smoking media, higher taxes and achieving smokefree movies without anyone even using an e-cigarette. Doing so (without e-cigarettes) would have saved even more lives – 7.0 million fewer lives lost and 91.4 million fewer life years lost.
The centrality of the first assumption is demonstrated by the fact that, using the Levy et al model (which they provided me as a spreadsheet) requires that e-cigarettes be more dangerous than cigarettes (about 120-130% more dangerous) to end up having a net negative population health impact. This is because they assume huge drops in smoking cigarettes.
In other words, all that this paper shows is that if a lot fewer people smoke, there will be a lot fewer premature deaths from smoking. It contributes absolutely nothing to the discussion of the efficacy of e-cigarettes for harm reduction.
It would be like someone asking what would happen to melting ice sheets if we were to be able to bring greenhouse gasses back to pre-industrial levels in 10 years. The calculation is possible but the results would not contribute anything to public policy because, like the Levy paper, the assumptions are discordant with reality.
Finally, in the Conclusion of their paper Levy et al state that “tobacco industry documents reveal an industry strategy of ‘divide and conquer’ focused primarily on fostering divisions within the tobacco control community regarding modified risk products. Indeed, the tobacco control community has had divided approaches to e-cigarettes, and in the process may have lost focus on cigarettes, the most deadly form of nicotine delivery ... Most important, an e-cigarette substitution strategy provides the justification to redouble efforts to target cigarette use, as called for by the WHO Framework Convention for Tobacco Control.” The authors are, of course, welcome to their opinion. But nothing in this paper provides an empirical support for this argument.