This study adds to the limited research on vape use in Canadian post-secondary students. We found that, while vaping is common among all university students, it is particularly high among the youngest students. Indeed, 41.0% of teenage students had self-reported vaping in their lifetime and one-fifth (19.7%) of them have vaped in the past month. These rates are comparable to Ontario data from 2019, where 23% of students in grades 7 to 12 had vaped in the past year and 33% of students in grade 12 had vaped in the past 12 months. ³ Other top risk factors for lifetime and past month vape use in the current study included male gender, alcohol, cigarette, cannabis, and cocaine use, and having many (16+) sexual partners.

Our finding that males were more likely to vape than females is in keeping with research from college students in the U.S.^{10bibr11-11782218211052059-12} This result may not be surprising, given that males are also more likely to smoke cigarettes ²⁴ and experience greater subjective reward from nicotine than do females. ²⁵ Research also suggests that, unlike cigarette smoking, vaping advertisements tend to focus predominantly on males, ²⁶ which likely contributes to their higher use in males. Additionally, we found that past and current vape use was highly correlated with alcohol, cannabis, cocaine, and tobacco use. Cigarette smoking has also been shown to be a top predictor of vape use in college students in the U.S.^{10bibr11-11782218211052059-12} and Europe^13,14 and past and current vape users were more likely than non-vapers to use alcohol, cannabis, and cocaine in U.S. college students. ²⁷ Our findings also coincide with data from the 2017 Canadian Tobacco, Alcohol and Drugs Survey, where a strong association was found between vaping and cannabis, alcohol, and illicit drug use among Canadians aged 15 to 24 years. ²⁸ However, unlike the nationally representative Canadian data, our findings show a much higher prevalence of current vape use among university students. Whereas 6.2% of Canadians aged 15 to 24 years had self-reported vaping in the past month, ²⁸ we found that 19.7% of teens and 11.1% of students 20 to 25 years had vaped in the past month. The higher prevalence of vape use in the current study, which is based on more recent data, is at least partially attributable to the growing popularity and use of vapes in the past few years. ³ It is also plausible that high risk-taking behavior, that is characteristic of university students,^6,7 may also explain some of the variation in vape use in this study. Lastly, compared to university students who had never had sex, those with 16+ partners were far more likely to have ever vaped in their lifetime and in the past month. Although research examining this relationship is limited, especially in post-secondary students, this finding has been shown in adolescent populations. A nationally representative study of high school students in the U.S. found that vape users were more likely than nonusers to have ⩾ 4 sexual partners in their lifetime and to be currently sexually active. ²⁹ Similarly, in the Healthy Kids Colorado Survey, middle school and high school students who were current vapers were more likely than nonusers to have had more than 1 sexual partner in the last 3 months. ³⁰

When the regression analysis was limited to university students who were not of legal age to purchase vaping products in Ontario (ie, 17-18 years), only cigarette smoking and cannabis use remained correlated with both lifetime and past month vape use. However, the correlations remained similar to the full sample. For example, alcohol use was highly and significantly correlated with lifetime vape use. Similarly, although not statistically significant, the odds of vape use (both lifetime and past month) were higher for males than females, and for those who used cocaine compared to those who did not, but the wide confidence intervals reflect the smaller sample size and lower statistical power of the secondary analysis. Further exploration of these correlations with larger samples of younger teenagers are needed in future research. While the relationship between vape use and cigarette smoking is well established,^31,32 recent evidence suggests that poly-substance use is increasing among youth and that vaping has played a key role at increasing it. ³³ In a systematic review and meta-analysis, vaping has also been found to be significantly associated with cannabis use. ³⁴

There are 3 limitations that should be considered when interpreting the results of this study. The first is that the data were captured cross-sectionally, meaning that associations between potential risk factors and vape use were measured at 1 point in time. However, to increase our confidence in the proper time order, we used past month vape use as one of our dependent variables and many of our independent variables were fixed at some point prior to variation in the dependent variable (eg, age, race, sex, childhood family structure, maternal education). Nonetheless, given the cross-sectional nature of the survey, we are only able to assess correlates of vape use in university students and could not investigate causal relationships. Second, our findings on correlates of vape use in university students cannot be generalized to post-secondary students across Canada as data were limited to a single university in London, Ontario. Additionally, 75% of our sample consisted of females, which is considerably higher than what is representative of the Western University student population at 56%. ³⁵ While this may have resulted in a biased sample, limiting the extent to which conclusions can be drawn from the data, our findings with respect to gender and vape use coincide with other studies on this topic. Our large sample of female university students may not also be that surprising, as a recent survey of undergraduate students at Western University consisted of 74% females. ³⁶ Third, our response rate of 6.8% was low and may limit the reliability of the results. We cannot also rule out self-selection bias, whereby students more interested in the topic of risk-taking behaviors were the ones more likely to complete the survey. However, research suggests that response rate bias is more concerning in univariate analyses of demographic characteristics and behaviors, but when assessing associations between variables using multivariate analysis, there is little evidence of bias from low response rates for most outcome variables. ³⁷

Our study adds to the limited research on vape use among post-secondary students in Canada. Findings from this research suggest that lifetime and past month vape use is far more common among teenage university students, males, those who drink alcohol, smoke, use cannabis or cocaine, and who have a history of many sexual partners. Among those who are not of legal age to purchase vaping products in Ontario (ie, students 17-18 years), vaping is highly correlated with cigarette smoking and cannabis use. It is hoped that these findings can be used by the university and local public health unit to develop future vaping awareness and prevention campaigns and to effectively target such activities to the most vulnerable students. Future research should expand these findings to other post-secondary institutions across Canada and utilize longitudinal designs to determine which risk factors increase the likelihood of first time vape use or vaping on a more regular and frequent basis. Such studies can provide public health policymakers and decisionmakers with the additional evidence they need to develop policies and programs aimed at curbing vape use among Canadian youth.