Although this is a relatively small study, as the authors acknowledge, it indeed helps to elucidate some clarity on some central issues. One such issue is that that the study contributes to confirming that the continued use of both e-cigarettes and tobacco cigarettes, i.e. “dual use”, does not appear to significantly reduce the harms of smoking. Arguably, this is not “news”. One very large longitudinal study (1), followed 24 959 men and 26 251 women, aged 20–49 years, screened for risk factors of cardiovascular disease in the mid-1970s, screened again after 3–13 years, and followed up throughout 2003. The authors of this substantial longitudinal concluded that:
“Long-term follow-up provides no evidence that heavy smokers who cut down their daily cigarette consumption by >50% reduce their risk of premature death significantly. In health education and patient counselling, it may give people false expectations to advise that reduction in consumption is associated with reduction in harm.”
In retrospect, therefore, it have been somewhat misleading for an important evidence review like the 2014 Cochrane Review of E-Cigarettes (2) to make one of its primary outcome measures: a 50% reduction in tobacco consumption. Some observers are still, erroneously and misleadingly, publically claiming that “when people vape, they smoke less, even if they don’t manage to quit altogether. In other words, harm is reduced” (3). This claim, in fact, does smokers a significant dis-service.
Other reviews (4; 5) have highlighted, indeed, that even the so-called “light smoking” of only one to four cigarettes per day still risks producing significant harm, so, the results of this new study, in respect of dual use are, arguably, not that surprising. As the authors state, users of e-cigarettes must appreciate that, for there to be an appreciable benefit to their health, they need to fully switch away from tobacco cigarettes.
Unfortunately, it appears that, currently at least, the significant majority of e-cigarette users: firstly, either stop using them, finding that the devices fail to satisfy their cravings, are “not like smoking” a cigarette and are “messy fiddly devices” (6; 7); or, secondly, continue to dual use (8) along with tobacco cigarettes. Thus, the technology and chemistry involved needs to improve, if e-cigarettes are to fulfil the promise that some believe they have in truly competing with tobacco cigarettes.
The results here confirm, however, that a full switch to e-cigarettes, or nicotine replacement therapies, should significantly reduce exposure to the important cancer-causing toxins tested in this study – clearly, good news, in terms of cancer. However, the claim in the Cancer Research UK Press Release that “the long term effects of these products will be minimal” (9) is premature, and arguably, unscientific. The study could only test for a relatively limited number of the total of known relevant harmful substances: almost entirely related to cancer. It did not test for, for example, other important biomarkers, related to oxidative stress and the vascular system, that other studies using human subjects have (10), and which have indicated to expert toxicologists a “substantial exposure” and a concerning potential for harm, although, still less than from tobacco cigarettes (11).
Still other studies using human subjects, looking at different issues than this new study, have identified suppression of a significant number genes related to immunity and respiratory risks (12), and more recently, findings suggestive of inflammation and subsequent cardiac risk (13; 14).
This new study under review here, though helpful, is only part of the puzzle that is “e-cigarettes” – further, long term studies, following e-cigarette users for a prolonged period of time, tracking not just issues mostly related to cancer, but other specific respiratory and cardiac risks, are still required, before anyone can confidently claim that the harmful effects of switching purely to e-cigarettes are “minimal”. Further, as the authors indicate, it tells us nothing regarding the efficacy of e-cigarettes, which can currently only be described as either: very weak, at best (15): or detrimental to chances of cessation, at worst (16).
One of the observations regarding this new study is that, probably due to the predominant interests of the funder Cancer Research UK, its primary outcome measures were related to risks of cancer. Therefore, what the study did not consider are the potential cardiovascular effects of e-cigarettes, and the non-cancer respiratory effects. CDC data (17) demonstrates, importantly, that basically as many people die prematurely from the cardiovascular effects of smoking tobacco (160,000) as from cancer effects (163,700), so, if we then add on the premature deaths of the non-cancer lung disease (113,100), it becomes clear that the health effects of smoking are, unfortunately, very much more than those purely related to cancer.
‘‘All views are my own and do not necessarily reflect those of my employer”
Competing interests: No competing interests