Investigating the effect of e-cigarette use on quitting smoking in adults aged 25 years or more using the PATH study

Abstract

Background: Part of the evidence on harms and benefits of e-cigarettes concerns whether using e-cigarettes encourages smokers to quit.  With limited results from controlled trials, and weaknesses in much epidemiological data, we addressed this using nationally representative prospective study data, with detailed accounting for factors associated with quitting. Methods: Analyses used data for adults aged 25+ years from Waves 1 to 3 of the US PATH study. Separate analyses concerned follow-up from Waves 1 to 2, 2 to 3 and 1 to 3.  The main analyses related baseline ever e-cigarette use (or e-product use at Wave 2) to having quit at follow-up, adjusting for predictors of quitting derived from 55 candidates.  Sensitivity analyses omitted adults who had never used other products, linked quitting to current rather than ever e-cigarette use, used modified values of some predictors using later recorded data, or (in Wave 1 to 3 analysis only) also adjusted for quitting by Wave 2. Results: In the main analyses, unadjusted odds ratios (ORs) of quitting for ever e-cigarette use were 1.29 (95% CI 1.01-1.66), 1.52 (1.26-1.83) and 1.47 (1.19-1.82) for the Wave 1 to 2, 2 to 3, and 1 to 3 analyses.  These estimates reduced after adjustment, to 1.23 (0.94-1.61), 1.51 (1.24-1.85) and 1.39 (1.11-1.74).  The final models, including between six and nine predictors, always included household income, everyday/someday smoking, wanting to smoke after waking and having tried quitting, with other variables included in specific analyses.  Quitting rates remained elevated in e-cigarette users in all sensitivity analyses. ORs were increased where other product users were omitted.  Adjusted ORs of quitting for current e-cigarette use were 1.41 (1.06-1.89), 1.30 (1.01-1.67) and 1.56 (1.21-2.00). Conclusions: The results suggest e-cigarettes may assist adult smokers to quit, particularly in individuals not using other nicotine products, and who are current e-cigarette users.