Tobacco Center Faculty Blog

Samir Soneji and colleagues just published a meta-analysis of 9 longitudinal studies that examined the effect of e-cigarette use on subsequent cigarette smoking behavior.  Each of these 9 studies started with kids who had never smoked a cigarette and compared the odds that they would go on to smoke cigarettes later (usually a year later) among kids who were and were not using e-cigarettes at baseline (the beginning of the study).  They found that the pooled odds ratio for subsequent cigarette initiation was 3.62 and for current (30 day) smoking was 4.28.
 
These results are adjusted for a wide range of potential  confounding demographic, psychosocial, and behavioral risk factors.  Soneji and colleagues also do extensive sensitivity analysis to demonstrate that their findings are robust.
 

In March 2014 Lauren Dutra and I published Electronic Cigarettes and Conventional Cigarette Use Among US Adolescents: A Cross-sectional Study in JAMA Pediatrics.  This paper showed that those youth who experimented with cigarettes (i.e., answered “yes” to the question “Have you ever smoked a cigarette, even a puff?”) were much more likely to be established smokers (smoked 100 cigarettes) than youth who did not use e-cigarettes.  We concluded “Use of e-cigarettes does not discourage, and may encourage, conventional cigarette use among U.S. adolescents.”
 
In writing the paper, Lauren Dutra and I took care not to use the word “cause” and noted that cross-sectional studies do not allow causal conclusions because they are a snapshot in time.  (Of course, you cannot smoke your 100th cigarette before smoking your 1st cigarette, so reverse causation is not an issue in this case.)
 
Despite the care we took on this point, Farsalinos and Polosa criticized this paper on the grounds that one cannot conclude causation from a cross-sectional study.