Krishna Reddy, MD

Clinical and public health questions around e-cigarettes are timely and hugely important, and key policy decisions – with long-term implications – are being made now with limited data. We have aimed to project the impact of e-cigarette regulatory policies on the prevalence of e-cigarette and cigarette use and on downstream health outcomes among US youth and adults. During this award period, we have expanded our modeling methodology to include behavioral transitions between various states of e-cigarette use and dual use of e-cigarettes and combustible cigarettes. Specifically, we have leveraged data from the longitudinal Population Assessment of Tobacco and Health (PATH) Study. First, using PATH data, we developed Markov multistate models to estimate the probabilities of transition between various states of e-cigarette and cigarette use (never, former, current, dual product use) among US youth and adults, stratified by age and sex. We applied these transition estimates in the Simulation of Tobacco and Nicotine Outcomes and Policy (STOP) microsimulation model, projecting prevalence of e-cigarette use and cigarette use over time and validating STOP model projections with empirical data from subsequent waves of the PATH Study. We have written a manuscript describing this methodologic development. The manuscript received favorable peer review, was invited for resubmission after revisions, and is currently under review. Second, we have used the PATH data, behavioral transition estimates generated from the Markov multistate models, and the STOP microsimulation model to project e-cigarette use and cigarette use among US youth and adults in the following scenarios: (1) Status Quo; (2) additional E-Cigarette Tax; (3) additional Cigarette Tax; (4) additional Combined Tax for both e-cigarettes and cigarettes. In addition to the baseline behavioral transition estimates from the Markov multistate models, we have turned to the health economic literature for estimates of the impact of an e-cigarette tax and a cigarette tax on initiation and cessation of e-cigarettes and cigarettes among US youth and adults. We have applied these estimates in the tax scenarios of our STOP microsimulation model analysis. Our preliminary model results show the prevalence of e-cigarette use and cigarette use, separately among youth (ages 12-17 years) and adults (ages =18 years), in the four scenarios over a five-year period. Additionally, we have conducted a model-based analysis of disparities in tobacco use and the health consequences in high-risk groups in the US, namely, those of low socioeconomic status and those with serious psychological distress. We presented this work orally at an international conference and have drafted a manuscript. Our ongoing efforts include model debugging, updating the baseline behavioral transition estimates with the latest available data from the PATH Study, validating our microsimulation model results with empirical data from other nationally representative studies, and conducting sensitivity analyses around the impact of taxes.

Update: We have been investigating the projected impact of regulatory policies on e-cigarette and combustible cigarette use. During this award period, we have expanded our simulation modeling methodology to include behavioral transitions between various states of e-cigarette use and dual use of e-cigarettes and combustible cigarettes. This resulted in a manuscript that received favorable peer review and was invited for resubmission after revisions. Additionally, we have conducted a simulation model-based analysis of the impact of an e-cigarette tax, a combustible cigarette tax, or a combined tax on the downstream prevalence of e-cigarette and combustible cigarette use among US youth and adults.