The evidence that e-cigarettes inhibit quitting smoking cigarettes just keeps piling up; strong longitudinal study from Canada

Laurie Zawertailo and colleagues from the Toronto just published a well-done study, “Concurrent e-cigarette use during tobacco dependence treatment in primary care settings: Association with smoking cessation at 3- and 6-months,” in Nicotine and Tobacco Research.
 
This large study followed 6526 Canadians who were trying to quit smoking forward in time for 6 months.  They compared people who did and did not use e-cigarettes and found that smokers who used e-cigarettes were 30% less likely to successfully quit smoking at 3 months and half as likely to have quit at 6 months than those who did not use e-cigarettes. 
 
They also found no significant effect on reducing the number of cigarettes per day at either time.  Whether smokers were explicitly using e-cigarettes as part of the quit attempt also did not affect quitting success.
 
These results, including the fact that whether e-cigarettes are being used explicitly for quitting. are consistent with the meta-analysis that Sara Kalkhoran and I published in Lancet Respiratory Medicine (odds ratio [OR] 0.72, 95% CI 0.57 – 0.91).
 
Here is the abstract:
 

Introduction: Electronic cigarettes (e-cigarettes) are being used as cessation aids by many smokers despite a lack of empirical evidence regarding their safety and efficacy. We analyzed the association of e-cigarette use and smoking abstinence in a population of smokers accessing standard smoking cessation treatment (nicotine replacement therapy plus behavioral counseling) through primary care clinics in Ontario, Canada.
 
Methods: Participants were recruited through 187 primary care clinics across Ontario, Canada and were eligible for up to 26 weeks of brief behavioural counseling and individualized dosing of nicotine replacement therapy at no cost. Adjusted logistic regression models were used to examine the association between concurrent e-cigarette use and smoking abstinence at 3- and 6-month follow-ups.
 
Results: Of the 6526 participants who completed a 3-month follow-up 18.1% reported using an e-cigarette while in treatment. The majority of e-cigarette users (78.2%) reported using an e-cigarette for smoking cessation. At 3-month follow-up, e-cigarette use was negatively associated with abstinence after controlling for confounders (AOR=0.706, p<0.001, 95%CI=0.607-0.820). E-cigarette use was also negatively associated with abstinence at 6-month follow-up (AOR=0.502, p<0.001, 95%CI=0.393-0.640).
 
Conclusion: E-cigarette use was negatively associated with successful quitting in this large community sample of smokers accessing standard evidence-based smoking cessation treatment through primary care clinics, even after adjusting for covariates such as severity of tobacco dependence, gender and age. The findings suggest that concurrent use of e-cigarettes with NRT may harm cessation attempts.
 
IMPLICATIONS This study confirms previous findings from observational studies regarding the negative association between e-cigarette use and smoking cessation, but in a large cohort of smokers enrolled in an evidence-based treatment program. The implications of these findings are that concurrent use of e-cigarettes during a quit attempt utilizing cost-free evidence-based treatment (nicotine replacement therapy plus behavioural counselling) does not confer any added benefit and may hamper successful quitting.

 
The full citation is Zawertailo, et al.  Concurrent e-cigarette use during tobacco dependence treatment in primary care settings: Association with smoking cessation at 3- and 6-months.     Nicotine Tob Res (2016) doi: 10.1093/ntr/ntw218 First published online: August 31, 2016.  It is available for free here.