Researchers in Iran attempt a review of literature on e-cigarette with probably the idea to exploit their results for regulatory purposes. Unfortunately their effort is vain and leaves the results inconclusive.
Iran, not an e-cigarette friendly country
Iran is clearly in the list of countries not welcoming the e-cigarette, especially if this one vaporizes nicotine. As an Islamic country, the consumption of nicotine is condemned by the religious authorities. The sale of e-cigarettes is illegal and no specific regulation applies to the product. However, some stores do sell e-cigarettes but their high prices in shop and the absence of spare parts are prompt to discourage smokers from switching to vaping.
The logical consequence is that in Iran, there is no research addressing prevalence of e-cigarette use. A group of researchers at the Shahid Beheshti University of Medical Sciences in Tehran (Iran) investigated and reviewed published scientific literature and aimed at presenting a simple conclusion on the effectiveness of e-cigarette for quitting smoking or as a safe alternative for smoking.
The general context of their study was not disclosed in the manuscript but it could easily be imagined that such a review was elaborated for regulatory purpose.
A wrong methodological approach
Their approach is at least original even if not scientific. It consisted to gather and review all available papers dealing with e-cigarette between 2009 and September 2014, and to have a scientific panel of experts decide whether each paper was favourable or unfavourable with regard to the device.
The panel decided to reject unpublished and duplicate articles, they also considered with caution opinion papers and those that were seemingly irrelevant. A training period was dedicated to set up the methodological review under the supervision of the principal investigator.
The null hypothesis leading to a positive evaluation of the reference was that e-cigarettes were “effective for quitting smoking and not harmful without side effects on respiratory health“. If such a conclusion couldn’t be made by the panel, a negative rating was given to the publication. The search criteria in PubMed were: Electrical cigarette[Title] OR EC[Title] OR e-cigarette[Title]) OR ENDS[Title]
The researchers identified 149 papers, among which 137 were eligible according to the criteria decided for the expertise but only 69 were retained.
- 34.8% were in support of the null hypothesis, as an effective and non-harmful method for tobacco cessation,
- 65.2%% did not support the null hypothesis.
- 46.7% estimated e-cigarettes not effective for smoking cessation,
- 53.3% were inconclusive with regard to smoking cessation.
Misleading conclusions: e-cigarette are harmful and do not help smokers who quit
In the light of their conclusions the authors believe that using e-cigarettes is harmful. They do not consider that enough evidence is available to consider e-cigarette as an help for smoking cessation. They raise the question of the popularity of e-cigarette use for smoking cessation with regard to the paucity of reliable scientific support. Two articles previously written by the same first author showed that e-cigarettes were not recommended to quit smoking, a finding that finally converges with the WHO’s recommendations.
A null hypothesis too restrictive
The null hypothesis is too restrictive: “effective for quitting smoking” + “not harmful” + “without side effects on respiratory health”. The chances to meet all the criteria at the same time is much weaker than to meet each criterion, individually. Hence, with almost 1/3 positive entries against 2/3 negative entries (because the do not comply with one or more criteria), my opinion is that the e-cigarette doesn’t do too bad. Imagine that in a crowd you had one chance out of three encounters to meet a woman who is single + rich + pretty… wouldn’t you be glad?
From a statistical point of view, the arithmetic operation on papers presenting the e-cigarette in a positive or a negative way does not constitute a sufficiently robust scientific approach to validate the hypothesis, at least on the short term. The reason is that it offers a snapshot of the state-of-the-art of this discipline at one moment. The issue is that the moment reflects a combination of political context and funding opportunities. that do not guaranty a neutrality in the investigation. In no case it could be used as a robust evaluation of the absolute value of the e-cigarette.
Information present in the article do not allow re-analysis of the data
On the 149 references gathered by the researchers only a few of them are provided in the reference list. And even if their criteria were robust enough to accept of reject the null hypothesis, the information contained in the manuscript make it impossible to further evaluate the accuracy of their methodology.
I just performed the same inquiry onPubMed and it returned 6300 entriescorresponding to all the authors’ criteria (Electrical cigarette[Title] OR EC[Title] OR e-cigarette[Title]) OR ENDS[Title]). I removed the term “ENDS” that can also have other meanings than the acronym for “electronic nicotine delivery system” and I changed “electrical cigarette” for “electronic cigarette”, the query returned 3200 references ((Electronic cigarette[Title] OR EC[Title]) OR e-cigarette[Title]). When I added to the previous query all the terms in plural, I obtained 1261 abstracts (representing approximately 2 months of intense reading and probably one year to go through the full texts) .The graph of abstract counts as a function of the year indicates that since 2012, the number of publications per year has been multiplied a factor 5 and should reach, by the end of this year more than 750 references.
However, many references dealing with e-cigarettes have conflicts of interest that are or not disclosed by the authors. With higher amonts of publication, the number of publications regarded as “junk science” also increases, which makes review of literature more and more tricky, each year.
Better turn to more robust reviews of literature
Even if it may be tempting for national officials to consider such a review of literature data as a basis to regulate the e-cigarette in their country, I would highly recommend not to do so and to prefer a more careful reviewing exercise like, for example, the lastCochrane Review 2016 on e-cigarette, where the scientific approach is better constraint. With a little attention, the public will also notice that conclusions are drastically different.