Methods: We analyzed data from the first four waves (2013-2018) of the Population Assessment of Tobacco and Health (PATH: N=5,065) a prospective longitudinal study of youth (ages 12-17) in the United States. We estimated a survey-adjusted multinomial model (n=4,534) predicting current (30-day) e-cigarette (n=249), cigarette (n=190), and dual use (n=92; ref: no use) at Wave 4. Independent variables included earlier dummy-coded tobacco use patterns (e-cigarette only, cigarette only, and dual use) at waves 1-3, and sociodemographic characteristics (sex, age, race/ethnicity, parental tobacco use and marital status, and academic performance).
Results: At Wave 1, e-cigarette use predicted of cigarette use at Wave 4 (OR=5.25), even after controlling for tobacco use types at Waves 2 and 3. Wave 2 e-cigarette (OR=4.41), cigarette (OR=3.25) and dual use (OR=5.24) was associated with cigarette use at Wave 4. By Wave 3, strong lagged effects were found for virtually all use types (ORs>5)
African American youth (ref: White) were much less likely to be current e-cigarette (OR=.13), cigarette (OR=.38) or dual users at Wave 4, American Indian youth were much less likely to become current e-cigarette and cigarette users at Wave 4, and Latino youth were less to become e-cigarette users at Wave 4. Youth of divorced parents had twice the odds (OR=2.09) of being dual users, and parental tobacco use (OR=2.59) was associated with double the odds of cigarette use at Wave 4.
Conclusions and Implications: We found that e-cigarette use was associated with greater odds of tobacco use four years later, even after controlling for later use at Waves 2 and 3. E-cigarette use was positively associated with other use patterns later in adolescence, reinforcing the idea of e-cigarettes may be a gateway to other tobacco use. It is clear from this nationally representative study that any early nicotine product use is problematic for later use, and e-cigarettes are no exception. Risk of e-cigarette use in particularly prevalent among White youth with lower odds among African American, Latino and American Indian Youth. Unlike cigarette use, e-cigarette use does not seem to be driven by parental use. Limitations of the study include relatively small cell sizes for dual use patterns and some racial categories (e.g. Native American) and no assessment of other types of tobacco use (e.g. cigarillos). Moreover, e-cigarette use has expanded since 2018. Future research should explore the extent to which adolescent use patterns predict tobacco dependence in young adulthood. Public health efforts should focus on preventing early use of e-cigarettes and other tobacco products in early adolescence.