Association of electronic cigarette vaping and subsequent smoking relapse among former smokers.

Introduction:
This text provides an analysis of the association between e-cigarette use and smoking relapse among former smokers in the Population Assessment of Tobacco and Health (PATH) study. The study investigates whether e-cigarette use in former smokers is associated with lower, higher, or no difference in odds of relapse back to combustible cigarette smoking. The analysis is conducted separately for recent and long-term quitters of combustible cigarettes at baseline to investigate odds of smoking relapse attributable to early and protracted post-quit e-cigarette use, respectively.

Key Points:

* The study uses data from the first two waves of the PATH study, a nationally representative longitudinal study of tobacco product use in the US.
* The analysis focuses on former smokers and classifies them as recent or long-term quitters based on their response to a question about the duration since they completely quit smoking cigarettes.
* The study defines smoking relapse as a positive response to the question "Do you now smoke cigarettes?" and measures the frequency and intensity of smoking in relapsers.
* The study classifies e-cigarette use into four categories: never use, prior use, current occasional use, and current regular use.
* The study finds that in recent quitters, e-cigarette use is not associated with smoking relapse at follow-up. However, in long-term quitters, both prior use and current regular use of e-cigarettes are associated with higher odds of subsequent smoking relapse.
* Among relapsers, baseline e-cigarette vaping is not associated with smoking frequency or intensity at follow-up.
* Sensitivity analyses found no evidence that associations between baseline e-cigarette vaping and smoking relapse at follow-up were influenced by variation in e-cigarette device characteristics, reasons for e-cigarette use, e-cigarette use frequency, or length of time since quit smoking at baseline.

Main Message:
The study provides evidence that e-cigarette use more than one year after quitting smoking is associated with increased risk of future smoking relapse. This association follows a gradient, with smoking relapse likelihood at one-year follow-up being lowest in baseline never-vapers, moderate in baseline prior or current occasional vapers, and highest in baseline current regular vapers. The study suggests that further research is needed to determine the causality of this association and to inform whether extended post-quit vaping in long-term former smokers should be encouraged or potentially discouraged due to smoking relapse concerns.

Dai H, Leventhal AM. Association of electronic cigarette vaping and subsequent smoking relapse among former smokers. Drug and Alcohol Dependence. 2019;199:10-17. doi:10.1016/j.drugalcdep.2019.01.043