In this study, we sought to identify which adolescents progress to regular electronic cigarette (e-cigarette) use (without cigarette smoking), which adolescents become dual users of both types of cigarettes, and how dual use develops across time.

Adolescents (N = 1808) from public high schools outside Philadelphia, Pennsylvania, completed in-classroom surveys at wave 1 (fall 2016, beginning of ninth grade) and at 6-month intervals for the following 36 months (fall 2019, beginning of 12th grade).

A sequential processes growth mixture model identified 4 conjoint latent classes: later, rapid e-cigarette uptake (class 1: n = 230); no use of e-cigarettes or combustible cigarettes (class 2: n = 1141); earlier, steady e-cigarette uptake (class 3: n = 265); and dual use of e-cigarettes and combustible cigarettes (class 4: n = 204). Using a rich set of potential risk factors, multinomial logistic regression assessed the likelihood of belonging to each conjoint class compared with the comparison class (dual use). Adolescents in the dual use class were characterized by a greater number and severity of e-cigarette and combustible cigarette risk factors. Adolescents in the 2 e-cigarettes–only classes were characterized by either e-cigarette–specific risk factors (earlier onset) or no risk factors (later onset). The no use class had an absence of risk factors for e-cigarette and cigarette use.

This study provides new prospective evidence for distinct patterns and profiles of adolescents who progress to current e-cigarette use, including adolescents who were initially cigarette smokers. The findings have implications for prevention intervention timing, tobacco product focus, content, and the adolescent subgroups to target.

在这项研究中，我们试图确定哪些青少年开始定期使用电子烟（电子烟）（不吸烟），哪些青少年成为两种类型香烟的双重使用者，以及双重使用如何随着时间的推移而发展。

宾夕法尼亚州费城以外公立高中的青少年 ( N = 1808) 在第 1 波（2016 年秋季，九年级开始）和接下来的 36 个月（2019 年秋季，12 年级开始）中每隔 6 个月完成了课堂调查年级）。

连续过程增长混合模型确定了 4 个联合潜在类别：稍后，电子烟的快速吸收（类别 1：n = 230）；不使用电子烟或可燃香烟（第 2 类：n = 1141）；更早，稳定的电子烟吸收（第 3 类：n = 265）；电子烟和可燃香烟的双重使用（第 4 类：n= 204）。使用一组丰富的潜在风险因素，多项逻辑回归评估了与比较类别（双重用途）相比属于每个联合类别的可能性。双用类青少年的特点是电子烟和可燃香烟风险因素的数量和严重程度更高。仅吸电子烟的 2 类青少年的特征是电子烟特定的风险因素（较早发生）或无风险因素（较晚发生）。不使用类别没有电子烟和香烟使用的风险因素。

这项研究为目前使用电子烟的青少年（包括最初吸烟的青少年）的不同模式和特征提供了新的前瞻性证据。研究结果对预防干预时间、烟草产品重点、内容和目标青少年亚群有影响。