Samir Soneji and his colleagues have just published the best-done model for assessing the effects of e-cigarettes on population health so far (including the one Sara Kalkhoran and I published). Their model accounts for the effects of e-cigarette use on youth and young adult initiation as well as cessation in adult smokers. The model is based on extensive population data on smoking behavior and how it evolves over time as well as the health effects of smoking. Most impressively, they use their baseline data to predict future behavior that was subsequently observed and show that the model is accurate. This is the first time anyone has done such a validation, which is a particular strength of the study.
What they find is that even making very optimistic assumptions about the effects of e-cigarettes on smoking cessation and assuming a 95% reduction in risk associated with e-cigarette use, the availability of e-cigarettes is associated with net population harm (1.5 million years of life lose based on e-cigarette use patterns in 2014).
They found about 80 new smokers for ever one that quit even making the optimistic assumption that smoking cessation increased among e-cigarette users.
More realistic assumptions about the effects of e-cigarettes (that the depress smoking cessation for most smokers and are more than 5% as bad as cigarettes) make the net negative effect even bigger.
Here is the abstract:
BACKGROUND:
Electronic cigarettes (e-cigarettes) may help cigarette smokers quit smoking, yet they may also facilitate cigarette smoking for never-smokers. We quantify the balance of health benefits and harms associated with e-cigarette use at the population level.
METHODS AND FINDINGS:
Monte Carlo stochastic simulation model. Model parameters were drawn from census counts, national health and tobacco use surveys, and published literature. We calculate the expected years of life gained or lost from the impact of e-cigarette use on smoking cessation among current smokers and transition to long-term cigarette smoking among never smokers for the 2014 US population cohort.
RESULTS:
The model estimated that 2,070 additional current cigarette smoking adults aged 25-69 (95% CI: -42,900 to 46,200) would quit smoking in 2015 and remain continually abstinent from smoking for ≥7 years through the use of e-cigarettes in 2014. The model also estimated 168,000 additional never-cigarette smoking adolescents aged 12-17 and young adults aged 18-29 (95% CI: 114,000 to 229,000), would initiate cigarette smoking in 2015 and eventually become daily cigarette smokers at age 35-39 through the use of e-cigarettes in 2014. Overall, the model estimated that e-cigarette use in 2014 would lead to 1,510,000 years of life lost (95% CI: 920,000 to 2,160,000), assuming an optimistic 95% relative harm reduction of e-cigarette use compared to cigarette smoking. As the relative harm reduction decreased, the model estimated a greater number of years of life lost. For example, the model estimated-1,550,000 years of life lost (95% CI: -2,200,000 to -980,000) assuming an approximately 75% relative harm reduction and -1,600,000 years of life lost (95% CI: -2,290,000 to -1,030,000) assuming an approximately 50% relative harm reduction.
CONCLUSIONS:
Based on the existing scientific evidence related to e-cigarettes and optimistic assumptions about the relative harm of e-cigarette use compared to cigarette smoking, e-cigarette use currently represents more population-level harm than benefit. Effective national, state, and local efforts are needed to reduce e-cigarette use among youth and young adults if e-cigarettes are to confer a net population-level benefit in the future.
The full citation is Soneji SS, Sung HY, Primack BA, Pierce JP, Sargent JD. Quantifying population-level health benefits and harms of e-cigarette use in the United States. PLoS One. 2018 Mar 14;13(3):e0193328. doi: 10.1371/journal.pone.0193328. eCollection 2018. It is available for free here.
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