What the data on gateway say today
With respect to gateway, one article has stated that: “There was strong evidence for an association between e-cigarette use among non-smokers and later smoking (OR: 4.59, 95% CI: 3.60 to 5.85) when the results were meta-analysed in a random-effects model. However, there was high heterogeneity (I2=88%).” The authors further concluded in the review: “However, the results do not provide strong evidence of a gateway effect.”[2]
An expert roundtable discussion funded by Cancer Research UK came to the following conclusion on gateway: “The group felt that there was no convincing evidence in the UK to support the premise that e-cigarettes are acting as a gateway product in either adult or youth populations. Data have shown that only a small percentage of adult never smokers (0.3%) and youth never smokers (0.5%) are current daily vapers.”
One delegate pointed out that if e-cigarettes were in fact a gateway product, one would surely see a rise in the overall population smoking rates since the introduction of e-cigarettes. However, many studies have shown the opposite to be true, with current smoking rates in England declining from 19.9% of adults over the age of 18 in 2010 to 15.5% in 2016.[3]
Furthermore, Cancer Research UK has concluded as follows: “And the good news is that smoking rates and the perceptions around the acceptability of smoking have declined in young people, even since the introduction of e-cigarettes. So, it doesn’t seem like e-cigarettes have interfered with the promising drop in levels of smoking in young people.”[4]
A recent analysis in Belgium of annual survey data showing an increase in the use of e-cigarettes examined the link between vaping and smoking amongst Flemish youth.[5]
The survey data, collected by the Vlaams expertisecentrum Alcohol en andere Drugs (VAD) in 2021-2022, was analysed in collaboration with the Vlaams Instituut Gezond Leven.
The analysis reached the following main conclusions:
- Vaping among the underaged who have never smoked is low, with 91.2% of those who have never smoked reporting that they also have never vaped;
- The use of e-cigarettes by those who reported never smoking is temporary or occasional;
- Those who report regular vaping are mainly those who currently smoke or have done so previously; and
- E-cigarette use by the underaged is strongly linked to the smoking behaviour of their parents.
In a news release on the analysis, Vlaams Instituut Gezond Leven’s tobacco expert concluded that underaged vaping “is a nuanced story, in which two parameters are very important: the frequency of use and the link with (previous) smoking.”[6]
Recommendations for future study design to assess gateway effect
- Usage classification should reflect more representative real world user behaviours (e.g. is one puff in the last 30 days a true measure of a smoker or a vaper?)
- Questionnaires should include biochemical verification with nicotine or N-(2 cyanoethyl) valine, CEVal, being two useful markers to assess nicotine usage and cigarette usage respectively
- Negative controls would confirm if associations were causal
- Include specific product information (e.g. nicotine strength/flavours used in product) from the study participants to enable mechanisms of association to be confirmed
