Re: E-cigarettes help up to 22 000 smokers in England quit each year
West et al: Commentary on the utilisation of “unreliable assumptions”.
The calculations made West et al letter published in the journal Addiction (1) utilise, in stage 5 of their calculations, the Cochrane Review of Electronic Cigarettes (2) and “Real World” observational follow-up data from Brown et al (3). These are central to calculating the next step in their reasoning: the proposed superior efficacy of electronic cigarettes over “licensed nicotine products” in smoking cessation.
As the West et al Step 5 states:
“Evidence from RCTs and from surveys in England indicate that using an e-cigarette in a quit attempt increases the probability of success on average by approximately 50% compared with using no aid or LNP bought from a shop – similar to use of a licensed medicine with limited behavioural support but less than medication plus specialist behavioural support.”
1) The Cochrane Review clearly states itself that: “We could not determine if EC was better than a nicotine patch in helping people stop smoking because the number of participants in the study was low.”
2) It further states: “. . . under the GRADE system the overall quality of the evidence for our outcomes was rated ‘low’ or ‘very low’ because of imprecision due to the small number of trials. A ‘low’ grade means that further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. A ‘very low’ grade means we are very uncertain about the estimate.”
3) Indeed, Jamie Hartson-Boyce, one of the co-authors of the Cochrane Review, with co-reviewer (4), has very recently stated that:
“Electronic cigarettes and other electronic nicotine delivery devices — These are currently not prescribable in most countries and have a very small evidence base. A Cochrane review showed weak evidence that electronic cigarettes containing nicotine were more effective for helping people to quit smoking than those without nicotine.”
4) A further recent systematic critique of The Cochrane Review (5) states that:
“Overall the quality of the evidence appeared to be low. The studies were from developed countries only. The limitations include the small number of studies and study participants in the RCT and inadequate data from both RCT and observational studies to assess all outcomes that were planned.”
5) A further, very recent meta-analysis of the available RCTs (6) in fact goes further:
“Limited low-quality evidence of a non-statistically significant trend toward smoking cessation in adults using nicotine e-cigarettes exists compared with other therapies or placebo. Larger, high-quality studies are needed to inform policy decisions.”
The calculations made by West et al, utilising the data available, appear to be a case of “Evidence about electronic cigarettes: a foundation built on rock or sand?” (7). However, they make the statement that others (8) have made calculations utilising “unreliable assumptions” (1). This appears to be contradictory with their own methods, which rely on weak and poor quality data, and which produce subsequently, their own, unreliable assumptions.
Subsequent to Step 5, the words “assumed” and “estimated” are utilised on multiple occasions, and all of these are calculations are unreliable, due to the nature of the data. However, as Professor West notes with regard to calculations, “. . . the numbers of users of electronic cigarettes successfully quitting is not as many as some e-cigarette enthusiasts claim” (9). Moreover, as per the West et al letter, the devices are having a devastating effect on “foot fall” at Stop Smoking Services, which all agree currently hold the highest level of efficacy for smoking cessation.
2) McRobbie H, Bullen C, Hartmann-Boyce J, Hajek P. Electronic cigarettes for smoking cessation and reduction. The Cochrane database of systematic reviews. 2014;12:Cd010216.
3) Brown J, Beard E, Kotz D, Michie S, West R. Real-world effectiveness of e-cigarettes when used to aid smoking cessation: a cross-sectional population study. Addiction (Abingdon, England). 2014;109(9):1531-40.
8) Kalkhoran S, Glantz SA. Modeling the Health Effects of Expanding e-Cigarette Sales in the United States and United Kingdom: A Monte Carlo Analysis. JAMA internal medicine. 2015.
Competing interests: No competing interests