The use of e-cigarettes has been spreading for more than a decade, especially among young people and adolescents, causing considerable concern among health professionals and institutions. Although they are marketed as consumer products, outside the efficacy and safety requirements that apply to medicines, the e-cigarette industry promotes the idea that they are useful for smoking cessation or for reducing the harm caused by tobacco. 

In the randomised clinical trial just published by a group of Finnish researchers led by Anna Tuisku, 458 smokers were randomised into three groups who received 12 weeks of smoking cessation treatment: one group received e-cigarettes and nicotine refill liquids plus tablets with a placebo, a second group was given varenicline tablets (one of those used for smoking cessation) and e-cigarettes without nicotine, and a third group received e-cigarettes without nicotine and tablets with a placebo. All participants attended eight individual visits with a nurse using the motivational interviewing model, a common type of behavioural intervention in smoking cessation treatment. Neither the study participants nor their therapists knew who was receiving e-cigarettes with or without nicotine, and who was taking tablets with varenicline or placebo. 

Six months after starting treatment, smokers who were given access to nicotine-containing e-cigarettes showed levels of tobacco abstinence (at least 7 days without smoking) close to those among those treated with varenicline and non-nicotine e-cigarettes. After one year, however, only those treated with varenicline still showed higher levels of abstinence than the control group, while the use of nicotine-containing e-cigarettes had not maintained a statistically significant favourable effect. 

The duration of pharmacological treatment of smoking is usually limited to a few weeks or a few months. In contrast, it has been found that many smokers who use e-cigarettes with the intention of quitting smoking continue to use them after one year, whether they remain smoke-free or have relapsed to tobacco use. The study did not mention what percentage of smokers continued to use e-cigarettes after 12 weeks of treatment, which would be important to know given the health risks of continued use.   

According to the information provided by the authors, the study was not funded by the tobacco or e-cigarette industry, a potential conflict of interest that affects much research on the use of e-cigarettes. However, the clinical trial was conducted with financial support from the pharmaceutical company that exclusively marketed varenicline until a few years ago, although the authors state that the study was conducted entirely independently. 

This is a randomised clinical trial, in principle well conducted, comparing three treatment groups (an e-cigarette (EC) with nicotine group, a varenicline plus EC without nicotine group, and a placebo control group) for smoking cessation in heavy smokers (heavy and long term smokers) interested in quitting and includes intensive motivational support. Results show that both EC with nicotine and varenicline increase cessation compared to EC without nicotine. At one-year follow-up, 28% of smokers using nicotine-containing ECs remained abstinent, as did 37.9% of those using varenicline and 19.9% of the control group.  

The results are relevant and a plain reading indicates that varenicline and EC with nicotine are equally effective in smoking cessation. However, the clinical relevance of the efficacy of varenicline is much higher (18 percentage points) than that of EC with nicotine (8.1 percentage points), beyond statistical significance which is most likely not reached due to a methodological problem. The trial seems designed to test the superiority in efficacy of nicotine-containing EC or varenicline over placebo, not to compare the equivalence of treatment with nicotine-containing EC and varenicline. For this type of equivalence comparison, a larger sample size is needed. And these details are not included in the main article, and the appendices and supplementary materials could not be consulted. 

Although the results are promising for the use of nicotine-containing ECs in smoking cessation consultation, even though they have lower efficacy than varenicline, the trial has other limitations. Firstly, the article assumes that ECs are much safer than conventional cigarettes, so the authors do not consider continued use of ECs as a complication. A recently published meta-analysis shows that, for several outcomes, ECs have disease risks indistinguishable from conventional cigarettes, and for others, although lower, the risks remain substantial. The second problem lies in the nature of the trial participants. It is well known that trial participants differ in important respects from non-participants. Smokers who participate in trials attended by smoking cessation clinics are a self-selected minority of smokers who may differ in important respects from smokers who do not seek professional assistance. Therefore, these results may not be generalisable to all smokers who quit, as 65-75% of ex-smokers have quit without professional help.  

The article does not provide sufficient evidence to include EC as a smoking cessation therapy in routine health care until it is approved as a smoking cessation therapy by the European and Spanish competent authorities. To our knowledge, no CE companies (mostly part of the tobacco industry) have presented their products as therapeutic interventions.