Most studies of the association between e-cigarette use and smoking and nicotine cessation have been conducted with the earlier generation e-cigarettes, which do not deliver nicotine as effectively as the fourth generation e-cigarettes pioneered by Juul. (These e-cigarettes use protonated nicotine [also called nicotine salts] to increase nicotine delivery to the user.) Our meta-analysis of these earlier studies, however, did find that daily e-cigarette use was associated with with increased likelihood of stopping smoking whereas non-daily e-cigarette use with associated with less stopping smoking (with no overall effect among all e-cigarette users). Now, Natalie E. Quach and her colleagues at UCSD have published a high quality longitudinal study of the association between intensity of e-cigarette use and smoking cessation among people using modern fourth-generation e-cigarettes. Their paper “Daily or Nondaily Vaping and Smoking Cessation Among Smokers” followed people in the FDA/NIH Population Assessment of Tobacco and Health from 2017 to 2021 to examine the association between e-cigarette use and stopping smoking cigarettes and stopping both cigarettes and e-cigarettes among daily and non-daily e-cigarette users.
They found that “neither daily nor nondaily vaping was associated with increased smoking cessation, and each was associated with reduced tobacco abstinence.”
In addition, in reaching this conclusion they determined that it was crucial to control for compounding variables i.e. characteristics of people who use e-cigarettes which were different from characteristics of people who didn’t use e-cigarettes. Indeed, when they failed to control for confounders they found e-cigarette use was positively associated with stopping smoking, which does not reflect the actual effects of e-cigarette use on smoking behavior.
In particular, they found:
In this representative cohort study, as in prior studies, unadjusted abstinence rates suggested that daily e-cigarette vaping was associated with increased long-term smoking cessation. However, once confounders were adjusted for, daily vaping at baseline was not associated with increased cigarette abstinence at follow-up as compared with similar smokers who did not vape.
… when major confounders were controlled for, the estimated effect size indicated a decrease in future smoking cessation among smokers who vape, whether they vaped daily or nondaily. Furthermore, e-cigarette use was associated with a large and significant decrease in future abstinence from tobacco use (cigarettes or [e-cigarettes]). These nationally representative data suggest that vaping prolongs both smoking and nicotine dependence among US smokers. [emphasis added, citations dropped]
This study adds important evidence that e-cigarettes as used in the real world actually keep people smoking, so promote harm.
Here is the abstract:
Importance: An important public health goal is to increase tobacco cessation, but there is limited research on associations of vaping with tobacco cessation.
Objective: To estimate the association of vaping with long-term tobacco cessation among US cigarette smokers who used electronic nicotine delivery systems (ENDS; ie, e-cigarettes) in 2017.
Design, setting, and participants: This cohort study used a nationally representative sample of US cigarette smokers from the Population Assessment of Tobacco and Health cohort at wave 4 (2017) with follow-up at wave 6 (2021). Data were analyzed from June 2023 to June 2024.
Exposure: Wave 4 ENDS use: daily, nondaily, or no use.
Main outcomes and measures: The primary outcomes were 12 or more months’ abstinence from cigarette smoking and 12 or more months’ abstinence from both cigarette and ENDS use, ascertained at wave 6. Propensity score matching was used to control confounding on 14 potential confounders, including interest in quitting, income, age, education, nondaily smoking, and presence of a smoke-free home.
Results: A total of 6013 smokers were included in the sample (3634 aged ≥35 years [weighted percentage, 65.2%]; 3182 female [weighted percentage, 46.5%]). Among smokers who vaped daily (228 individuals), an estimated 20.9% (95% CI, 15.0% to 26.8%) were abstinent from cigarette smoking at follow-up, compared with 14.3% abstinence (95% CI, 13.0% to 15.5%) among smokers who did not vape (5070 individuals) and 12.6% abstinence (95% CI, 9.8% to 15.4%) among smokers who vaped nondaily (715 individuals). Compared with similar propensity score-matched smokers who did not vape, smoking cessation was 4.1 percentage points lower among those who vaped daily (95% CI, -11.9 to 3.6 percentage points; P = .30), a nonsignificant difference. Smoking cessation was 5.3 percentage points lower among those who vaped nondaily (95% CI, -9.1 to -1.5 percentage points; P = .01) compared with similar propensity score-matched controls. Considering abstinence from both smoking and vaping, compared with matched controls, smokers who vaped daily had lower abstinence at follow-up by 14.7 percentage points (95% CI, -20.2 to -9.2 percentage points; P < .001), and those who vaped nondaily had lower abstinence by 7.2 percentage points (95% CI, -10.7 to -3.8 percentage points; P < .001).
Conclusions and relevance: In this representative cohort study of US smokers who used ENDS, neither daily nor nondaily vaping was associated with increased smoking cessation, and each was associated with reduced tobacco abstinence, suggesting that careful adjustment of confounding is critical in studies of ENDS and smoking cessation.
The full citation is: Quach NE, Pierce JP, Chen J, Dang B, Stone MD, Strong DR, Trinidad DR, McMenamin SB, Messer K. Daily or Nondaily Vaping and Smoking Cessation Among Smokers. JAMA Netw Open. 2025 Mar 3;8(3):e250089. doi: 10.1001/jamanetworkopen.2025.0089. PMID: 40042845; PMCID: PMC11883493. It is available for free here.
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