Aims: With the rising popularity of vaping among young people, evidence indicates that young people who vape are more likely than those who do not to subsequently take up smoking (i.e., the “gateway effect”). We estimated the future cancer burden among people who initially started vaping and subsequently smoked.
Methods: We used a Markov, dynamic cohort model to estimate the number of Australians who smoke tobacco and/or vape. Smoking and vaping uptake probabilities, as well as transition probabilities between smoking and vaping, were calibrated using data from the National Drug Strategy Household Survey from 2001 to 2022, adjusted for age and sex differences. We then estimated the number of people who subsequently smoked, out of those who had no prior smoking history but had exclusively vaped. Cancer cases and cancer-related mortality among these cohorts were estimated for 10 leading types of cancer: lung, larynx, oesophagus, liver, bladder, pancreas, stomach, colorectum, prostate and melanoma.
Results: For those who smoked after they had initiated vaping, the total cancer cases of the 10 types occurring over a 30-year period (i.e., 2022-2052) was estimated to be around 80,000 cases – with lung, colorectal and liver cancers accounting for nearly half, at about 39,000 cases. Total cancer cases occurring over an 80-year period (i.e., 2022-2102) was estimated to be around 2.1 million cases. Total cancer-related deaths over the same period was estimated to be around 800,000. Had they not smoked, the total cancer cases and cancer-related mortality occurring over the 80-year period would have been about 1.7 million cases and 520,000 deaths, respectively.
Conclusions: Using the preliminary findings, there would be a substantial future burden among those who subsequently smoke after initiating vaping. As today's young people age, cancer burden resulting from the gateway effect is anticipated to increase significantly.