Selya AS, et al. - The mutual correlations between e-cigarette use, conventional cigarette use, and nicotine dependence over time were gauged. The intent to was to investigate the link between e-cigarette use and later conventional smoking (both direct and via nicotine dependence) and the converse associations. It also identified the strongest pathways predicting each product's use. Nicotine dependence did not serve as a notable mechanism for e-cigarettes' purported effect on heavier future conventional smoking among young adults. It could be a mechanism for increases in e-cigarette use among heavier conventional smokers, consistent with e-cigarettes as a smoking reduction tool. Hence, it was reported that conventional smoking, and to a lesser extent its resulting nicotine dependence, were the strongest drivers or signals of later cigarette and e-cigarette use.

Methods

• Data was cumulated from 4 annual waves of a prospective cohort study.
• Path analysis modeled the bi-directional, longitudinal relationships between past-month smoking frequency, past-month e-cigarette frequency, and nicotine dependence.
• It was carried out at Chicago area, Illinois, USA.
• The enrollees constituted N=1007 young adult smokers and nonsmokers (ages 19-23).
• The measurements included frequency of 1) cigarettes and 2) e-cigarettes, which was the number of days in the past 30 on which the product was used.
• The Nicotine Dependence Syndrome Scale estimated the nicotine dependence to cigarettes.

Results

• There was no notable link between e-cigarette use and later conventional smoking, either directly (β=0.021, p=.081) or through nicotine dependence (β=0.005, p=.693).
• A positive association was detected between conventional smoking with later e-cigarette use, both directly (β= 0.118, p<.001) and through nicotine dependence (β=0.139, p<.001).
• The strongest predictors of each product's use was prior use of the same product.
• It was strong for conventional cigarettes (β=0.604, p<.001) but weak for e-cigarettes (β= 0.120, p<.001).
• Nicotine dependence moderately strongly speculated later conventional smoking (β=0.169, p<.001), but served as a weak predictor of later e-cigarette use (β=0.069, p=.039).