Longitudinal patterns of e-cigarette use initiation and progression to frequent vaping from mid-to-late adolescence to young adulthood.

Aims: This exploratory study aimed to describe longitudinal patterns of e-cigarette use initiation and progression to frequent use across mid-to-late adolescence and young adulthood and determine risk factors for and consequences of these initiation patterns.

Design: Using 12 waves of a prospective cohort data across 2014-2023, we identified latent classes with distinct patterns of timing of e-cigarette use initiation and frequent use progression (20 + days/month). We then estimated: (1) associations of baseline risk factors with membership in latent classes and (2) associations of latent classes with e-cigarette/other substance use frequency and e-cigarette dependence at a subsequent 1-year follow-up.

Setting: Southern California, United States.

Participants: Baseline e-cigarette never users [n = 2291; mean age (standard deviation) = 15.0 (0.4) years; 55.1% female; 44.6% Hispanic].

Measurements: Repeated self-reported e-cigarette use initiation and past-30-day frequency, other substance use and e-cigarette dependence.

Findings: Four distinct groups were identified: (1) early high school/gradual progression (13.9%); (2) late high school/gradual progression (4.3%); (3) young adulthood/quick progression (21.3%); and (4) low initiation risk/no progression (60.5%). In addition to two high school initiator groups with gradual progression to frequent vaping over 3 years, we identified the young adulthood/quick progression group who initiated e-cigarette use after high school and progressed to frequent use within 1.2 years. Late initiators who progressed quickly reported the highest prevalence of JUUL use as their first device (34.2%) and the highest levels of vaping frequency and e-cigarette dependence at the final assessment, compared with the other groups.

Conclusions: In the United States, there appear to be four distinct classes of developmental patterns of e-cigarette use initiation and progression to frequent use during mid-to-late adolescence and young adulthood, including a newly identified group characterized by late use initiation (post secondary school) and rapid progression (1.2 years) to frequent use. Rapid progression from late initiation to frequent use may be influenced by the widespread availability and usage of JUUL among US youth in 2018-2019.