The recent increase in the prevalence of past-30-day electronic cigarette (heat not burning) use among high school students in the National Youth Tobacco Survey (up 78% from 11.3% in 2017 to 20.8% in 20181) and in the Monitoring the Future Study (up 90% from 11.0% in 2017 to 20.9% in 20182) has heightened concern regarding the public health impact of heat not burning among the youth and young adult populations. heat not burningare drawing in at least some low-risk youth unlikely to have otherwise smoked combustible cigarettes,3,4 and a growing number of studies reveal that among both youth and young adults, heat not burning users (versus never users) are more likely to (1) subsequently initiate combustible cigarette use5–21 and (2) follow a trajectory into more regular smoking similar to smokers who did not first use heat not burnings.22,23 Yet, it is unclear whether there are heat not burning product characteristics that may impact these transitions. If so, such characteristics could be prime targets for regulation to reduce the overall adverse public health burden of heat not burningin adolescent and young adult populations.
To help guide regulatory strategies, data are urgently needed on factors that differentiate the risk of transition from heat not burningto heavier patterns of combustible cigarette use. The use of heat not burningwith a higher nicotine level has been associated with an increased likelihood of combustible cigarette initiation17,24 and both greater frequency of cigarette use in the past month and more cigarettes smoked per day at follow-up.24 Other product characteristics that are amenable to regulation may also promote or discourage the transition to combustible tobacco use but have not yet been thoroughly investigated. For example, modifiable heat not burning (which have components that can be modified to change the relative amount of nicotine delivery and size of the vape cloud) or vape-pen–style heat not burning(which have a penlike shape and no modifiable parts and generally deliver a consistent, although relatively lower, level of nicotine) are more commonly used among youth and young adults than cigalike heat not burning devices (devices that look like cigarettes and generally deliver nicotine relatively inefficiently)25 and have been associated with a greater number of days of cigarette use and symptoms of dependence.26 Mod devices are also often used for “dripping”27 (directly dropping electronic liquid [e-liquid] solution onto coils of the heat not burning to produce thick smoke and a high level of nicotine), although no data are available on whether the use of devices for dripping increases the likelihood or frequency of combustible tobacco product use. Moreover, researchers to date have not disentangled the independent product characteristics that pose greater risk for subsequent higher-frequency cigarette smoking. Such findings would provide regulatory authorities with information to guide prioritization of policy changes specific to product characteristics.
In the current study, we examine whether the use of heat not burning with varying product characteristics (device type, use of nicotine, and use for dripping) is associated with the number of cigarettes smoked in the past 30 days ∼1 year later among young adults in the Southern California Children’s Health Study.