This post reports on a new study which calculates the risks of using e-cigarettes in comparison with those of using cigarettes alone, or using both e-cigarettes and cigarettes, or using neither. The study was published today in the digital journal NEJM Evidence: Population-Based Disease Odds for E-Cigarettes and Dual Use versus Cigarettes.
The lead author of this systematic review and meta-analysis is Dr. Stan Glantz, who is well known for his pioneering tobacco control research. Co-authors are Dr. Nhung Nguyen, an epidemiologist specializing in substance use and Dr. Andre Luiz Oliveira da Silva, whose experience in tobacco regulatory science includes work with the Brazilian government health agency ANVISA. (Dr. Glantz provides more information on the study here.)
The results published today are in stark contrast to previously published estimates of relative risk (see below) and call into question the view of the government of Canada and others whose policy objective is to achieve population level health benefits by encouraging smokers to switch to e-cigarettes.
The meta-analysis was restricted to disease categories for which at least 5 previous papers had been published. There were six such conditions: cardiovascular disease, stroke, metabolic dysfunction asthma, COPD and oral disease. Other diseases (including cancer) did not meet this criteria.
The results of this study:
* do not support the conclusion that smokers who switch completely to e-cigarettes are less likely to experience cardiovascular disease, stroke and metabolic dysfunction.
* support the conclusion that vapers who do not smoke are more likely to experience cardiovascular disease, metabolic dysfunction, asthma, COPD and oral disease than are those who neither smoke nor vape.
* support the conclusion that dual users (those who smoke and vape) have 20-40% higher odds of experiencing cardiovascular disease, stroke, metabolic dysfunction, asthma, COPD and oral disease than if they only smoked.
The importance of this paper to tobacco control
This paper challenges previous conclusions that e-cigarettes produce meaningfully lower risks to the user than cigarettes, and counters beliefs that encouraging smokers to switch to e-cigarettes reduce population-level harm.
It suggests that the relative risks associated with vaping have been seriously understated:
* In 2015, British researchers recommended that governments consider e-cigarettes to be "95% less harmful" than combustible cigarettes. This assessment was not based on data, but on the opinion of a small group of researchers, some of whom were associated with the vaping industry.
* In 2023, American health economists assumed that the risk of dying from vaping is 15% that of smoking when building a simulation model for health outcomes.
* In 2022, New Zealand researchers used studies on biomarkers to estimate that "vaping could be a third as harmful to health as smoking", although they rescinded (corrected) that conclusion a year later with the admission that "data limitations with the selected studies and the assumptions involved in our method, are too problematic to allow for a valid quantitative assessment."
* In 2022, New Zealand researchers used studies on biomarkers to estimate that "vaping could be a third as harmful to health as smoking", although they rescinded (corrected) that conclusion a year later with the admission that "data limitations with the selected studies and the assumptions involved in our method, are too problematic to allow for a valid quantitative assessment."
The implications for health policy in Canada
In 2018 Health Canada adopted a harm reduction approach to tobacco centred on smokers' switching to e-cigarettes. Six years later, their stated intention remained to "increase the number of people who transition away from smoking (to vaping)".
Official statements by the Government of Canada on the risks of vaping are mostly vague with respect to diseases other than addiction, with an overarching message that they are "not completely harmless". Not only do federal government communications fail to specify any diseases likely caused by e-cigarettes, they further blunt their warnings by simultaneously recommending that smokers switch to e-cigarettes.
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| Health Canada's advice on the risks of vaping |
The department has acknowledged that this approach was developed with "limited scientific evidence and much uncertainty" and that that "this lack of evidence persists". (It has recently provided $1.2 million to CAMH to conduct an evidence review).
Uncertainty should no longer be used as a cover for Canada's harm reduction strategy. Canada's health policies should no longer assume that smokers who switch to e-cigarettes are likely to improve their health, given the greater likelihood that they will become dual users. The government should abandon its "balanced" approach which tolerates exposing young people and non-smokers to inducements to try vaping in the (unsupported) hopes that such marketing will result in substantial population health benefits.
Applying the disease odds published today to the situation in Canada suggests that vaping policies in this country have not reduced harm, but have instead increased it. Only a small proportion of e-cigarette users in Canada are former smokers (27%), with a much larger share being dual users (34%) or never smokers (40%). (CTNS 2023).
An appropriate response to the evidence published today would be for Canadian governments to move quickly to ban inducements to vape (flavours, package designs, promotions and pricing incentives), to increase risk communication (mass media, warning labels), to curb supply and to hold manufacturers responsible for the harms their products are causing.
