Factors Associated with Dual Use of Tobacco and Electronic Cigarettes: A Case Control Study

Background: Many electronic cigarette (EC) users reduce cigarette consumption without completely quitting. It is important to assess the characteristics and experiences of these users, commonly called "dual users", in comparison with EC users who have completely substituted smoking (non-smoking vapers).

Methods: A questionnaire was uploaded in an online survey tool. EC users were invited to participate irrespective of their current smoking status. Dual users were matched for age and gender with non-smoking vapers.

Results: From 19,441 participants, 3682 were dual users. After random 1:1 matching with non-smoking vapers (all of whom were former smokers), 3530 participants in each group were compared. Dual users had longer smoking history, lower daily cigarette consumption and similar cigarette dependence compared to non-smoking vapers. Their daily consumption was reduced after initiation of EC use from 20 to 4 cigarettes per day. Most of them were using ECs daily, however, more were occasional EC users compared to non-smoking vapers. Use of advanced (third generation) devices and daily liquid consumption was lower in dual users compared to non-smoking vapers. The most important reason for initiating EC use was to reduce smoking and exposure of family members to smoke for both groups, but higher scores were given to "avoid smoking ban in public places" by dual users compared to non-smoking vapers. The strongest predictors of being dual user from multivariate analysis were: higher risk perception for ECs (OR=2.27, 95% CI=1.40-3.68), use of first-generation EC devices (OR=1.98, 95% CI=1.47-2.66), use of prefilled cartomizers (OR=1.94, 95% CI=1.23-3.06) and occasional use of ECs (OR=1.62, 95% CI=1.21-2.17).

Conclusions: The results of this case-control study indicate that higher risk perceptions about, and less frequent use of, ECs was associated with dual use of ECs and tobacco cigarettes. Since this is a cross-sectional survey, which explores association but not causation, longitudinal studies are warranted to further explore the reasons for dual use.