Policy scenario of successful US ratification.

<p>Policy scenario of successful US ratification.</p

Policy scenario of US failure to ratify.

<p>Policy scenario of US failure to ratify.</p

Results of sensitivity analysis.

<p>Results of sensitivity analysis.</p

Probability of a positive total number of years of life gained varying the level of four key model parameters.

<p>Note: vs. = versus; Adj. = Adjusted.</p

Quantifying population-level health benefits and harms of e-cigarette use in the United States

<div><p>Background</p><p>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.</p><p>Methods and findings</p><p>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.</p><p>Results</p><p>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.</p><p>Conclusions</p><p>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.</p></div

Number of additional adult current cigarette smokers who quit for ≥7 years and additional adolescents and young adults who initiate cigarette smoking and eventually become daily cigarette smokers at age 35–39, all through the use of E-cigarettes.

<p>The mean of the distribution is shown as a solid circle and the 95% confidence interval is shown as a vertical line. Source: stochastic simulation (100,000 iterations). Note: Addt’l = Additional; Cig. = Cigarette. Estimates reported as text in the figure rounded to 3 significant digits.</p

Total number of years of life gained.

<p>Negative years of life gained represent years of life lost. The mean of the distribution is shown as a solid circle and the 95% confidence interval is shown as a vertical line. Source: stochastic simulation (100,000 iterations). Estimates reported as text in the figure rounded to 3 significant digits.</p

Data Sources of model parameters.

<p>Data Sources of model parameters.</p

Total number of years of life gained by relative harm of E-cigarette use compared to cigarette smoking.

<p>Total number of years of life gained by relative harm of E-cigarette use compared to cigarette smoking.</p

Population-level model to quantify benefits and harms of E-cigarette use.

<p>Superscripted letters refer to the columns in Tables A and B in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193328#pone.0193328.s003" target="_blank">S3 Appendix</a> for age- and age-group-specific parameter point estimates and 95% confidence intervals. Note: Δ = Change in; | = Conditional On; NATS = National Adult Tobacco Survey; NHIS = National Health Interview Survey; NSDUH = National Survey on Drug Use and Health; NYTS = National Youth Tobacco Survey; and Prob. = Probability.</p