Prospective estimation of the age of initiation of cigarettes among young adults (18-24 years old): Findings from the Population Assessment of Tobacco and Health (PATH) waves 1-4 (2013-2017).

Objectives: To prospectively estimate the age of cigarette initiation among young adults (18-24 years old) who were never cigarette users at their first wave of adult study participation overall, by sex, and by race/ethnicity given recent increases in cigarette initiation occurring in young adulthood.

Methods: Secondary analyses were conducted using the PATH restricted-use adult datasets among young adult never users of cigarettes in waves 1-3 (2013-2016) with outcomes followed-up in waves 2-4 (2014-2017). Interval censoring survival methods were used to estimate the age of initiation of (i) ever, (ii) past 30-day, and (iii) fairly regular cigarette use. Among never cigarette users when they first entered the adult study, interval censoring Cox proportional hazard models were used to explore differences in the estimated age of initiation of the three cigarette use outcomes by sex and by race/ethnicity, controlling for the effect of previous e-cigarette use and the total number of other tobacco products ever used (0-5 products) before cigarette initiation outcomes.

Results: Among the young adults who were never cigarette users at their first wave of adult participation, the highest increase in cigarette initiation occurred between 18 and 19 years old. By age 21, 10.6% (95% CI: 9.5-11.7) initiated ever cigarette use, 7.7% (95% CI: 6.1-8.1) initiated past 30-day of cigarette use, and 1.9% (95% CI: 1.4-2.5) initiated fairly regular cigarette use. After controlling for other tobacco products: (a) males were 83% more likely to initiate past 30-day cigarette use at earlier ages than females; (b) Hispanic and Non-Hispanic Black young adults had increased risk to initiate past 30-day cigarette use at earlier ages than Non-Hispanic White young adults (62% and 34%, respectively).

Conclusions: The substantial amount of cigarette initiation among young adults reinforces the need for prevention strategies among this population. Although, interventions are needed for all young adult populations, strategies should target 18-21-year-olds, with potentially differential prevention targets by sex and by race/ethnicity.