The rapid rise in the use of electronic nicotine delivery systems (ENDS) has catalysed a large volume of research into their health risks and impact on combustible cigarette smoking. ENDS have independent health risks, and long-term consequences of ENDS use are unknown given their relative novelty; however, current evidence suggests that these products are less harmful than combustible cigarettes in the short and medium term. Randomised controlled trials show that ENDS are effective for smoking cessation in the short term, but evidence of their real-world effectiveness is limited. Most observational studies have found no association between ENDS use and smoking cessation; a few studies have found that daily ENDS use is associated with increased smoking cessation. Thus, in certain contexts, ENDS could help smokers to quit smoking. However, approximately 50% of adult ENDS users concurrently use cigarettes (hereafter referred to as dual use), and dual use is associated with increased health risks. Identifying patterns of ENDS and cigarette use among dual users can determine the public health impact of ENDS and inform tobacco control efforts.
Analyses of the Population Assessment of Tobacco and Health (PATH) Study data examining 1-to-2 year transitions among adult dual users have shown that roughly 25% remain dual users and approximately 50% switch to exclusive cigarette use; only~5–7% of dual users switch to exclusive ENDS use and~6–12% quit using both products. However, the long-term stability of these transitions is unknown. Analyses of ENDS and cigarette use over multiple time points allow examination of the stability of use of both products among dual users.
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