The case of young people who use e-cigarettes infrequently: Who is this population? What becomes of them?

Background: Emerging data indicate that many adolescents and young adults ("youth") engage in infrequent, or occasional, e-cigarette use. However, little is known about this population as they are often subsumed into the broader "any past-30-day use" category used to define youth "current use." This study aimed to focus on infrequent e-cigarette use by youth, examining its correlates and transitional outcomes.

Methods: Participants were from a prospective cohort study of youth (aged 15-24 at baseline). Among youth who had used e-cigarettes, we classified "infrequent use" as using e-cigarettes ≤5 days in the last 30 days (n=273) and "frequent use" as using e-cigarettes ≥6 days in the last 30 days (n=278). Descriptive statistics, Markov modeling, and logistic regression were utilized.

Results: By the 12-month follow-up, 76.8% of those using infrequently at baseline remained in the "infrequent use" category, 6.3% reported no recent use, and 16.8% had escalated to the "frequent use" category. Among the youth using infrequently at baseline, those who did (vs. did not) escalate to frequent use by follow-up had higher baseline nicotine dependence and were more likely to have family members who used tobacco.

Conclusions: Infrequent e-cigarette use is extremely common, and often fairly stable, among young people. Prevention efforts must certainly attempt to reduce escalation and attend to both individual and interpersonal factors (e.g., nicotine dependence, family use). Yet prevention efforts must additionally attend to the case of continued infrequent use, given the high prevalence of people in this category and their regular exposure to e-cigarette harms.